FAQs

Most answers to questions about home energy use depend heavily on details for the specific home in question — the climate where the home is located, it's energy usage patterns, home size, configuration and features. For this reason, we can give general guidance here, but for a more definitive answer use the Home Energy Saver.

Not finding what you need here? Try DOE's Information Center.

General

  1. How can I save energy in my second home, which is unoccupied a large part of the year?
  2. What's the most common mistake people make in trying to save energy around the house?
  3. We don't own a home; we rent an apartment. What can we do?
  4. We have an older house. Which should we do first: insulate or replace the furnace?
  5. My neighbor's bills are much lower than mine, even though they have children, and are home more than we are. Why are my bills so high?
  6. What's the single biggest user of electricity in my house?
  7. I was trying to find an estimate of the expected savings of an ENERGY STAR New Home (30% better than Model Energy Code) versus an "average" existing home. Your estimates seem to be oriented to retrofits using ENERGY STAR equipment, as was clear once I got into the details. Have you also done, or do you have a reference on the savings with the ENERGY STAR new home? That would presumably come out somewhat better than the full retrofit case.
  8. How about energy savings in my car?
  9. What are the benefits of energy efficiency besides saving energy?

Heating, Ventilation and Air Conditioning

  1. How much energy can I save by using fans instead of my air conditioner?
  2. Should I use portable room heaters to lower my energy bills?
  3. What information can you give me on air-to-air heat pumps for the home?
  4. Does it pay to run a large duct from the outside of the house to the furnace to provide outside air for combustion? Contractors provided a passive supply of air along with the installation of our new furnace in St. Paul, Minnesota and we are wondering if it is worthwhile with a 30-year old furnace in Macomb, Illinois.
  5. How can I tell if the contractor who is putting in a new furnace is gouging me on the price?
  6. We have been very unhappy with our current heat pump and are wondering whether to install a new one or convert to natural gas. What factors should we consider?
  7. If I shut off my heater or air conditioner when I'm gone from the house, doesn't it cost more to heat or cool the house back to the right temperature once I return?
  8. Will installing a programmable thermostat reduce my heating and cooling consumption?
  9. My central air conditioning blows cool but not cold air and seems to be always running. I have heard that dirty coils in the condenser could cause this. Is this something I can check and clean myself and, If so how would I go about it?
  10. We are purchasing a new air conditioner and the contractor mentioned something about "duct sealing." What is this and would this be a good thing to do?

Comfort and Indoor Environment

  1. On windy days I can feel drafts coming from the baseboards in my house. How can I stop these drafts?
  2. Some parts of my house are never comfortable, no matter what I do. The rest of the house is fine, but one room is always too hot or too cold. Why is that, and what can I do to fix it?
  3. I've heard that if we make our house too tight, the air won't be healthy to breathe.
  4. I am trying to find some information concerning attic fans (i.e. the pros and cons).
  5. We have condensation water drops on the vents that blow air into our living room. We have central air and we live in Wellington, FL. What could cause this condensation?

Windows

  1. I keep getting ads in the mail for companies offering to replace our windows with "energy-efficient" windows. How much can these save me?
  2. Over the winter, fog appeared between the panes of my double pane windows, but during the summer it went away. Why did this occur?

Water Heating

  1. Is there any rating for electric water heaters? I would be interested in knowing the ratings for brands.
  2. What is the average setting on an electric hot water heater?
  3. If you turn your hot water heater off during the day, won't it cost more because you then have to heat up the whole tank and wait minutes before taking a shower? Also, isn't it kind of an inconvenience?

Computers

  1. We're putting in a home office. Do computers and fax machines really use that much energy?
  2. Should I leave my computer on all the time, or turn it off when not in use?
  3. I have a Powermac 8500/180 and am wondering what I can do to lower its energy use. You mention that some new computers have ENERGY STAR compatibilities. My computer was made in 1996. Please help, my energy bill skyrocketed the month I plugged the computer in.
  4. Do you really think my answering machine uses more electricity than my computer?

Lighting

  1. My utility company tried telling us to use more fluorescent lights to save energy, but I hate how fluorescent lights flicker when you turn them on and then make that annoying hum. And they make everything look sort of blue and cold. Isn't there anything better?
  2. Is it better to turn lights off when you leave the room? I heard somewhere that it uses more energy to turn lights off and on than to leave them running.

General

How can I save energy in my second home, which is unoccupied a large part of the year?

There are millions of second homes in the United States. Some of these are owned by "snowbirds" who spend summers in the north and winters in the south, and many others with vacation homes. An unoccupied home that is not properly put in "standby mode" could cost well over $1000 if left alone for the one or more seasons.

For cold-climate homes, turning the heat off (or at least way down) while away is a natural starting point. Of course, preventing pipe freezing is essential but it may be able to be done without unnecessarily heating the home (e.g. with proper draining, and/or tape heaters wrapped to the pipes, toilets, and traps in key areas). If this is not sufficient then turning the heat way down (e.g. to 40-45 degrees) should provide adequate freeze protection at much-reduced cost. Roof-mounted electric heating elements used to melt ice dams may not be needed if the home is unoccupied and unheated, because snow will not be melting and refreezing at the eaves.

For hot-climate homes, the air-conditioning should be left off when away. With no one living in the home and indoor temperatures equilibrated with outdoor temperatures, less (no) water is generated in the house from activities like cooking and washing, and the risk of condensation and mold formation is minimized. Be sure to minimize sources of moisture in the vacant home. If moisture is a concern, having a humidistat wired in series with the thermostat would be prudent. In some cases a more energy-efficient humidifier may be used independent of full-on air-conditioning.

North or south, there are many other things to keep in mind. Water-heaters and refrigerators/freezers can be turned off (be sure to leave the doors ajar). All appliance transformers and power supplies should be unplugged (e.g., printers, computers, phones, television set-top boxes, halogen lights, fountains). And don't forget to shut off the spa. One or two indoor lights can be left on timers to help create the illusion that the home is occupied; there are probably even timers with random schedules. Outside lighting may be desired for security, but consider installing motion sensors so that the lights will only go on (temporarily) when movement is detected near the home — this lower use will also reduce the likelihood that security lights will burn out while you are away. Be sure, of course, that those lights that are left on are energy-efficient fluorescents.

In all cases, it is wise to have someone check the home periodically while you are away.

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What's the most common mistake people make in trying to save energy around the house?

Common mistakes people make include:

  • letting the furnace or air conditioner salesperson sell them a unit that's much bigger than they need,
  • not getting the ducts checked for leakage when installing a new heating and cooling system,
  • thinking that "since heat rises, we only need to insulate the attic." Floors over a basement or crawlspace, walls and windows also matter.
  • not using ceiling and portable fans to improve comfort in the cooling season. They use very little electricity. Use them to circulate air in the house, tomake the house feel cooler by doing this, the thermostat setting for the air conditioner can be raised to 85°F, and still maintain the same comfort as the lower setting.

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We don't own a home; we rent an apartment. What can we do?

If a landlord pays the utility bills it should be easy to convince him or her to make efficiency improvements, since they will realize the economic benefits. If you pay the utility bills you are still not without hope, because there are inexpensive things that you can do to lower energy bills and make the home more liveable.

Water heating costs can be reduced by putting a blanket on the heater. Blankets typically cost less than $10 and can save between 10 and 40% of water heating costs. However, water heaters less than five years old already contain sufficient internal insulation, and should not be wrapped, otherwise they might overheat. You can also reduce water use and heating costs by installing low flow shower heads and faucet aerators.

Weatherstripping can reduce or eliminate drafts through windows and doors. It doesn't take long to install, increases comfort and reduces costs. Rope caulk provides a temporary seal during the winter months around windows that leak. You can remove this seal in the summer so that you can open and shut the windows. If the windows are very leaky, you can fit a piece of plastic over the window during the winter to form an inexpensive storm window.

Here are some other possibilities:

  • Seal and caulk major air leaks around windows, door, electrical outlets, plumbing fixtures and outside architectural features like chimneys.
  • Shade south and west glass with deciduous plants to keep the heat out during the summer.
  • Use fans with the air conditioner. By circulating the air you can set the thermostat up to five degrees higher and maintain the same comfort level.
  • Install compact fluorescent lights (CFLs) in frequently used fixtures. While CFLs are expensive, you can take them with you when you move.
  • Consider replacing the refrigerator if it is more than ten years old. New efficiency standards went into effect in 1993, and older units are typically two to three time more expensive to run than a new unit. If you have a second refrigerator in the garage, consider getting rid of it. Chances are it is an older, inefficient unit, and since garages are hot in the summer, the refrigerator is even more expensive to run.
  • If you have a long-term lease, or expect to be in a house for a while, it could be cost-effective for you to install major efficiency improvements with short pay-back times, such as insulation.

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We have an older house. Which should we do first: insulate or replace the furnace?

Whether you should insulate or replace a furnace first depends on the situation in the house. Factors that influence this decision are the age and efficiency of the furnace, and the amount of insulation currently present in the house.

In general it is more cost-effective to upgrade insulation than it is to upgrade the furnace. However, if the furnace is old, and you are planning on replacing it anyway, you might want to upgrade the furnace if you have to choose between the two options. The average lifetime for a furnace is between 15 and 20 years. The efficiency of furnaces has increased over the years, so the older a furnace is, the more likely that furnace is to be inefficient. The average efficiency of new furnaces has increased from 63% in 1972 to 83% in 1995. Older furnaces, and furnaces which are used a lot are more cost-effective to replace than newer or infrequently used furnaces. Also, if the house is insulated at the time of furnace replacement, it may be possible to buy a smaller capacity furnace and save money on the price. The same holds true for A/C and other heating and cooling equipment.

Typically older houses were built with poor levels of insulation. As insulation ages, it compresses, becoming less effective at preventing heat transfer. Dust and moisture also contribute to the aging process in insulation. In temperate areas, if the insulation level in the house is less than 6 inches, the most cost-effective action is to increase the insulation up to R-30. For areas with extreme hot or cold temperatures, it is cost-effective to increase the insulation up to R-42.

Here are approximate R-values of different insulation levels. The actual R-value of the insulation depends on the type and condition of the insulation, but these approximate values are helpful for judging whether adding insulation is the best plan for the house.

Insulation Level Approximate R-Value
3 inches R-9
6 inches R-19
10 inches R-30
13 inches R-42

You might want to check out the Home Energy Saver calculator. It allows a user to explore the costs and savings of replacing a furnace compared to adding additional insulation, making decisions of this sort easier.

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My neighbor's bills are much lower than mine, even though they have children, and are home more than we are. Why are my bills so high?

There are a number of factors that cause differences in energy bills, so comparing the one home's bill to someone else's is like comparing apples to oranges. The ages of major appliances, especially refrigerators and air conditioners, can make a dramatic difference in the bill. In addition, if a house leaks air like a sieve while a neighbor's house was just weatherized and insulated, it will have much higher heating and cooling bills. Other factors that can result in significant differences in bills are the number and kinds of lighting fixtures, thermostat settings for heating and cooling, the number of loads of laundry, old refrigerators out in the garage, and hobbies which result in electricity use.

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What's the single biggest user of electricity in my house?

If a house has central air conditioning, the air conditioner will probably be the biggest user by far. Although used only a few months of the year, the annual cost can be much greater than the annual cost of running a refrigerator, which is typically the next largest user. In hot climates, the annual air conditioner cost can exceed a thousand dollars. You can get a very rough idea of what an air conditioner is costing to operate by subtracting the electric portion of the energy bill in a spring month when the air conditioner isn't being used from the electric portion of the bill in the summer when you do use it. This gives you the monthly cost. Multiply this by the number of months the air conditioner is used to arrive at the approximate annual cost.

Refrigerators are typically the largest users in houses without air conditioning or in climates where the air conditioners are used only a few days of the month during the cooling season. If an refrigerator is more than ten years old, consider replacing it. New efficiency standards went into effect in 1992, and older refrigerators are typically two to three times more expensive to run than a new unit. For more information go directly to the American Council for an Energy-Efficient Economy's list of most efficient refrigerator-freezers.

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I was trying to find an estimate of the expected savings of an ENERGY STAR NEW HOME (30% better than Model Energy Code) versus an "average" existing home. The HES estimates seem to be oriented to retrofits using ENERGY STAR equipment, as was clear once I got into the details. Have you also done, or do you have a reference on the savings with the ENERGY STAR new home? That would presumably come out somewhat better than the full retrofit case.

A conservative estimate of energy consumed by average existing homes is 100 million BTUs per year, at a cost of about $1,280.

The energy consumed by the average new home is about 90 million BTUs for around $1,250. This consumption is driven largely by appliances and gadgets.

ENERGY STAR new homes are designed to save 30% of HVAC (heating, ventilation and air conditioning) and hot water. These two end uses typically make up around 60% of the total bill, so the ENERGY STAR new home will save about 20% of the total bill. These homes have no restrictions, or rules about the appliances and gadgets that the owners can bring in, so there are no savings in these areas.

If you were to retrofit an existing home with the equivalent measures used in an ENERGY STAR new home by making HVAC and hot water improvements and bringing in efficient appliances, you conceivably could realize greater savings than an ENERGY STAR New Home, depending on the quality of the retrofit job. The next question is: would it would be cost-effective to do so? Retrofits on existing housing are generally more expensive than incorporating the same efficiency measure into the construction of a new home, and they may not work as well, depending on the quality of work. Visit the Home Energy Saver calculator to see the potential savings from retrofiting the house.

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How about energy savings in my car?

Automobile energy efficiency information links:

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Heating, Ventilation and Air Conditioning

How much energy can I save by using fans instead of my air conditioner?

The basic notion is that moving air (from ceiling, whole-house, or portable fans) makes you feel cooler, so you can turn up the air conditioner thermostat or turn it off altogether. Whole-house fans are a potential substitute for air conditioning, since they move large amounts of air through the house and require open windows. Savings from using a whole-house fan can be large (it uses 20% or less of the energy of a central air conditioner on a per-hour basis, although they usually need to be used for fewer hours). Also a whole-house fan provides good comfort levels when it's not too humid or too hot outside (night time). Studies by the Florida Solar Energy Center (FSEC) show that ceiling fans can save energy if the occupants turn up the A/C thermostat. Unfortunately, most people don't adjust the thermostat. Often people leave them on even when no one is home, which can result in negative savings.

Research from FSEC indicates that whole-house fan savings are quite variable, ranging from about 10% to 65%. This range is due to the effect of climate; a milder climate will see savings toward the upper end of that range. FSEC found that if the air conditioning thermostat is set 2°F higher when using ceiling fans, the savings will be 14%. (With a higher thermostat setting, savings are higher.) If the thermostat setting is not changed, electricity consumption will actually increase by 15%. FSEC's survey of actual behavior showed no measurable savings from cooling fans (i.e. in energy terms, the ceiling fan and the A/C were a wash). There is at least one efficient ceiling fan that uses less energy and has an occupancy sensor (on some models). See: "New Ceiling Fan Takes Flight"

Bottom line: Fans can save energy if the air conditioning thermostat setting is increased and if the fans are turned off when no one is home. For more information, visit these articles:

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Should I use portable room heaters to lower my energy bills?

Graph showing the hourly heating costs of a central gas heater vs. electric room heaters.

With rising energy prices, it's tempting to think about using portable room heaters. It's also worth considering a programmable thermostat, if you don't already have one. If the central heat is electric, it would almost certainly be possible to save money by using portable electric heaters. In fact, part of the savings come because valuable heat isn't being lost in the ducts before it reaches the living area.

If the central heat is gas, you might be able to save money by using portable electric heaters, but it's not something to take for granted.

Local energy prices and desired comfort level will determine the answer. Also, a typical central furnace will provide about 20-times as much heat as a portable, depending on its efficiency. Keep in mind that even if the hourly cost of using portable electric heaters is lower than for the furnace, the home's overall power demand will dramatically increase, which contributes to regional power shortages that ultimately can trigger blackouts and price increases.

We've put together the following chart to help you find out how much a heating bill could be reduced by using portable electric heaters.

To use the chart, follow this four-step process:

  1. Find the home's gas price on the left hand vertical scale and read over to the right until you hit the scale marked "Your Heating Bill." This is the hourly cost of running a 100kBtu/hour central furnace.
  2. Next, find the electricity price on the horizontal scale and read upwards until you hit the yellow line corresponding to how many portable heaters the home would like have on at one time (one to five).
  3. Next read from this point over to the "Your Heating Bill" scale to find the hourly cost of running a typical 1000 Watt portable electric heater.
  4. Compare the two hourly operating costs to see which is lower.

In the illustrative example provided, a home paying $0.75/therm of gas and $0.25./kWh would save money if using two portable electric units. They would break even using three and would have an increased heating bill for using more than three portable heaters.

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What information can you give me on air-to-air heat pumps for the home?

Air-to-air heat pumps are basically air conditioners with the capability of reversing their cycle to provide heating in the wintertime. During the summer, air conditioners remove heat from the house, and shunt it outside. Air source heat pumps have a switching system that allows them to operate in reverse in the winter, removing heat from the outside air, bringing it into the house. Since air source heat pumps are not actually creating heat, but moving it from one place to another, they are less expensive to operate than electric resistance heaters, and depending on the costs of both natural gas and electricity, possibly gas furnaces as well.

Gas is sufficiently cheaper than electricity that an air source heat pump is generally more expensive to operate than gas furnaces. For those who are unable to receive gas services, the air source heat pump is probably the best bet.

One drawback to air source heat pumps is that they get less efficient when the outside air temperature gets colder. It is harder to extract the residual heat from colder air. Electric resistance furnaces become more cost effective when the average winter air temperature is below 30°F.

Another option is ground- or water-source heat pumps. These units extract heat from the ground by using an underground loop, or from water, through an open or closed loop. Since the average ground temperature hovers around 50°F year round for most of the United States, this is a very good source for heat in the winter, and cooling in the summer. Although putting in a ground loop is expensive and repairs can be costly, ground-source heat pumps are good options for some people.

For further reading, see Energy Savers Tips: Heating and Cooling.

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Does it pay to run a large duct from the outside of the house to the furnace to provide outside air for combustion? Contractors provided a passive supply of air along with the installation of our new furnace in St. Paul, Minnesota, and we are wondering if it is worthwhile with a 30-year old furnace in Macomb, Illinois.

Most older furnaces are provided with combustion air from ducts leading into the furnace closet, or from openings to either the crawlspace or the attic, depending on the furnace location. To determine whether a furnace needs additional combustion air, look into the furnace closet. Using a flashlight, look at the walls and ceiling in the closet. You should see one of two things. There might be registers (or simple openings) to what look like ducts on the walls near or in the ceiling, or near the floor of the closet. Alternately, the ceiling of the closet might be open to the attic. If any of these are the case, the furnace is getting sufficient combustion air, and you do not need to worry.

If you do not see any ducts or openings, then check the door to the furnace closet. As long as the door is undercut by about 3/4 to one inch, the furnace can get plenty of air. Again, no problem, unless the house is very airtight.

The reason to provide extra combustion air is to prevent a backdraft where combustion gases are coming into the house rather than exiting through the flue. This is a very dangerous situation when it occurs, and can cause serious health problems, as well as death from carbon monoxide poisoning.

The fact that the furnace is thirty years old leads me to believe that it should get plenty of combustion air, unless you have had problems with backdrafts in the past. Most older houses have a lot of air leakage through the walls of the house, sufficient to provide combustion air for furnaces, water heaters and fireplaces. If you have recently altered the house in a way that could reduce air leakage, such as installing wall insulation where previously there was none, or if you installed house wrap while replacing siding, you might consider adding a duct to provide combustion air. If the water heater is gas, and is inside the house (rather than in the garage), check the air supply for its combustion as well.

This is more of a safety issue than an efficiency issue, so there won't be substantial monetary savings from providing outside air for combustion.

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How can I tell if the contractor who is putting in a my new furnace is gouging me on the price?

What you're experiencing is a major problem with large appliances that require contractors for installation. Scary as this may seem, there is no price list available in this type of situation. Prices can vary widely by contractor or area. It is even difficult to get wholesale listings from manufacturers, since they may charge different amounts to different contractors. If a local home repair store carries the brand of furnace you are interested, you can get a general idea of the unit cost. Unfortunately this does not cover labor and installation costs.

The best way to figure out if a contractor presents a reasonable bid is to shop around. Before you sign a contract, get several bids from different contractors. Five to seven would be ideal. For each bid, get all of the details in writing, and make sure the bids are comparable. Be careful if one of the bids is dramatically lower than all of the others. Make sure that the same work is actually being bid on. In addition, check with the local Better Business Bureau and find out if any of the contractors have complaints against them, and get details about complaints if you can.

There are a lot of good contractors who do quality work for reasonable prices. However there are also a lot of contractors doing shoddy work, and contractors who overcharge consumers.

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We have been very unhappy with our current heat pump and are wondering whether to install a new one or convert to natural gas. What factors should we consider?

A decision about whether to reinstall a heat pump depends on what is causing the poor performance of the current heat pump. It could be because the heat pump is really not meeting the heating needs, or because you have expectations based on previous experience with other types of furnaces.

There can be several causes of unsatisfactory heat pump performance:

  • Inadequate capacity to meet a home's heating load
  • Improper installation or servicing, such as improper refrigerant charge or air flow over the indoor coil
  • Leaking, uninsulated, or badly designed duct system

Unfortunately, most of these problems cannot be easily diagnosed by the homeowner, so it is best to have a qualified heating and cooling contractor check out the system. At a minimum, the system should be serviced annually by a contractor. If this does not seem to solve the problem, the contractor should thoroughly seal and insulate the duct system. Finally, if the problem still persists, the contractor can calculate the home's heating load to determine if the current unit has adequate capacity.

If the heat pump runs constantly, and the house is still uncomfortably cold, you might want to consider converting to natural gas, provided that theheat pump is fully charged, and operating properly. Have the heat pump serviced to confirm the unit is fully charged with refrigerant, and has no other mechanical problems. Since air-source heat pumps rely on the outdoor air for the warmth used to heat the house, they are not the optimal choice in really cold climates. In some areas, winter air temperatures are so cold that the heat pump is unable to extract sufficient heat to increase the temperature of the house up to the thermostat setpoint, even with continual operation. When the outside air is below 35°F, air-source heat pumps operate below their rated efficiencies, reducing the savings compared to a more efficient unit. You might want to consider switching to a ground-source heat pump in this situation. Ground-source heat pumps take heat from the ground, or from a water source such as a lake or well. These areas typically have very stable temperatures (approximately 50°F) year-round, enabling the heat pump to work at optimum efficiency.

Its also possible that you might be dissatisfied due to misunderstandings about the way that heat pumps operate. Understanding how they work and finding ways to work around their limitations can alleviate the problem.

Heat pumps produce lower temperature heat than a furnace, maintaining warmth in the house by operating longer. This lower temperature means it takes longer to heat up the house. Many people are accustomed to using furnaces in this manner. They are often disappointed with the performance of a heat pump. Heat pumps heat best when they are connected to a thermostat kept at a steady temperature, and allowed to cycle on and off to maintain a constant temperature.

If the occupant is been accustomed to the flow of hot air from the furnace, they may be disappointed in the air temperature coming from the heat pump. Once again, this is because of the lower temperatures. It doesn't mean that the house is colder, overall. However, areas near registers may now seem drafty, because the exiting air is closer to the body temperature. Placing deflectors on registers to direct air away from places where you linger will help.

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If I shut off my heater or air conditioner when I'm gone from the house, doesn't it cost more to heat or cool the house back to the right temperature once I return?

The rate of heat transfer from the house to the outside, or vice versa, is dependent partly on the temperature difference between the house and outside. More heat is transferred when the difference is greater, so it takes more energy to keep the house at 72°F when it is 40°F outside than to heat the house back up to 72°F after you return.

With air conditioning systems, the equipment runs at peak efficiency when it operates for long periods. Cooling the house back to the comfortable temperature will use less electricity than the unit would use cycling on and off for short periods to maintain the set temperature. If the house takes too long to get back to a comfortable temperature, you might investigate getting a programmable thermostat, and set it to start heating or cooling the house an hour or so before you return. You could also set the thermostat back, to a lower temperature for heating, or a higher one for cooling, while you are gone, rather than turning it off completely.

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Will installing a programmable thermostat reduce my heating and cooling consumption?

Yes, programmable thermostats can reduce the energy used for air conditioning or heating by 5 to 30% IF they are properly programmed. Just installing the thermostat isn't enough; you need to enter a schedule designed to be sure the heating and cooling systems do not run when not needed, and are set back when the comfort needs are more flexible.

Programmable thermostats, while not always digital, save money by turning the air conditioner to a higher setting (or heater to a lower setting) when no one is present in the house, or in the evenings when it is cooler. You can achieve the same savings without the programmable thermostat, but you would have to remember to change the thermostat every day when you leave the house, and turn it down every night when you go to bed. In addition, if the occupant is using the thermostat to regulate the heater, the occupant would wake to a cold house. The programmable thermostat does all of the remembering for you once it is set. A sample of a heating schedule you might program into a thermostat is:

  Time Heating Temp.
Wake up 6:00 am - 9:00 am 68°F
Leave 9:00 am - 5:30 pm 60°F
Evenings 5:30 pm - 11:00 pm 68°F
Sleep 11:00 pm - 6:00 am 60°F

This way the house is always comfortable and the occupantcan save money on heating. A similar schedule can be made for air conditioning.

  Time Cooling Temp.
Wake up 6:00 am - 9:00 am 75°F
Leave 9:00 am - 5:30 pm 80°F
Evenings 5:30 pm - 11:00 pm 75°F
Sleep 11:00 pm - 6:00 am 78°F or off

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My central air conditioning blows cool but not cold air and seems to be always running. I have heard that dirty coils in the condenser could cause this. Is this something I can check and clean myself and, If so how would I go about it?

There are a couple of things that can cause the symptoms you describe.

  1. You're right, the condenser may be dirty.
  2. There may be inadequate air flow around the condenser.
  3. There might be a leak, and the unit is out of refrigerant.
  4. The duct system might be leaking.

Things to do:

  1. Have unit serviced annually by qualified heat/cool contractor.
  2. Check the condenser. Go outside to the condensing unit, make sure that plants are trimmed at least two feet away from the top and sides of the unit. Make sure there are no leaves, dryer lint, lawn trimmings etc., stuck on or around the unit. Turn off the electricity to the air conditioner. Take a garden hose with a high-pressure nozzle (we're not talking firehose pressure however) and spray the condenser coils from the inside, forcing debris to the outside. Repeat the process from the outside, forcing any remaining debris inside. You are trying to knock out any dust, dirt, leaves, etc., that may have accumulated between the heat exchange fins. If any of the fins have been bent so that airflow is impeded, carefully take a thin blunt object like a wooden popsicle stick and straighten the fins. You might want to do this once or twice a year, to keep everything working optimally.
  3. Check the ducts. First do a pressure test. While the air conditioner is operating, go to each register and make sure that air is coming out. If there is no airflow from a register, or noticeably less, there is probably a major hole or disconnection along that duct passageway. Second, do a visual check of the ducts if possible. Most houses have leaky ducts, even new houses. Typically, leaks occur at bends, joints, and at register connections.

    Ducts can be disconnected by a simple bump when storing the luggage away in the attic. A disconnected duct wastes energy by heating or cooling the attic or crawlspace instead the home. In addition, pollutants and dust can be sucked into the house through a disconnected return duct. If you find a disconnected duct, reconnect it with sheet metal screws and mastic for metal ducts or zip-ties and butyl-backed tape (not duct tape, which degrades rapidly) for flexible ducts. If you wish, you can hire contractors to go over the entire duct system, sealing it for leaks. This will help lower heating and cooling costs.

  4. If neither of these things helps with the cool but not cold air coming from you unit, call an air conditioner contractor. He or she will be able to determine if the air conditioner has the proper refrigerant charge. Sometimes air conditioners are undercharged when first installed, sometimes there is a leak, allowing refrigerant to escape. A pressure test of the coils will determine which is the problem. You might want the contractor to clean the interior (evaporator) coils at the same time. Dust on these coils can reduce airflow, reducing efficiency.

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We are purchasing a new air conditioner and the contractor mentioned something about "duct sealing." What is this and would this be a good thing to do?

The duct systems in most houses leak. Leaks can be as small as pinholes or tiny cracks and as large as completely disconnected ducts. However, any leak is wasteful, since it allows conditioned air to escape into the attic, basement, or crawlspace. Duct sealing is a process of stopping leaks by physically patching all joints in the duct work. A new aerosol method is under development at Lawrence Berkeley National Laboratory, which would seal ducts without the need for a laborer to manually reach and plug every leak.

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Comfort and Indoor Environment

On windy days I can feel drafts coming from the baseboards in my house. How can I stop these drafts?

The best way to prevent drafts in a house is to stop the air from penetrating the outside shell. Typically, air comes in through cracks along the foundation, near the exterior of the chimney, water faucets and electrical outlets, and along doors and windows. A good quality outdoor caulk will prevent air flow through these areas. For cracks larger than 1/4 inch, fill the gap with insulation or some other filler material, then caulk over the area.

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Some parts of my house are never comfortable, no matter what I do. The rest of the house is fine, but one room is always too hot or too cold. Why is that, and what can I do to fix it?

This problem is probably caused by bad air ducts and/or poor insulation and windows in that area. Air ducts can be functioning poorly due to bad design, inadequate insulation, or air leaks. These problems reduce the amount of conditioned air reaching a room. Leaking and disconnected ducts waste the energy intended for heating or cooling by losing energy to the attic, basement or crawlspace, and contribute to indoor air pollution by increasing dust in the house or by drawing exhaust fumes from gas appliances back into the house.

Ducts can become disconnected or develop leaks in many different ways. One is accidental bumping, which happens when someone moves around the ductwork. In addition, over time duct tape can degrade and ducts, especially those under the flooring of houses, can simply fall apart. Disconnected ducts are not only a problem in old housing-the ducts in new houses are often accidentally disconnected during construction. Have the ductwork inspected and make sure any connections are airtight, and held together with zip ties, or sheet metal screws and mastic to create a good seal.

Also, if the uncomfortable room is at the end of a long duct run with lots of turns and connections, it may not get adequate air flow. A qualified heating and cooling contractor should be able to check out the duct system and make sure it is functioning properly. If you've checked out the ducts and determined they are not the problem, then the problem can probably be solved by insulating the ceiling, walls, or floor, or by replacing the windows with energy-efficient models.

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I've heard that if we make our house too tight, the air won't be healthy to breathe.

If you're building a new house, this can be a real concern. The architect should be able to design adequate ventilation as part of the plan. But if you have an older house, there are usually enough ways for air to get into the house that tightening up will save you energy but still leave an adequate supply of fresh air. If you are concerned that the house does not have adequate ventilation during certain times of the year, you can get more information about home ventilation at Energy Federation Incorporated (EFI) or the Home Ventilating Institute (HVI). Or, you may download an LBNL report on residential ventilation systems. Simply click on the report title under "Publications."

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I am trying to find some information concerning attic fans (i.e. the pros and cons).

Line drawing of a house showing the location of ridge vents and soffit or eave vents.

Mechanical ventilation is typically accomplished with a small fan located on a dormer vent. These fans are usually hardwired into a house's electrical system and are controlled by a thermostat. They usually draw electricity in the range of 2 to 70 kWh per year, depending on local weather conditions and the attic temperatures. The cost of this energy of course depends on the local price of electricity.

Approximately one square foot of ventilation is recommended for every 150 square feet of floor area. You would have to check the specifications of the particular fan you are considering to determine the equivalence to regular vents.

One alternative to mechanical venting is a combination of ridge vents and eave or soffit vents (see diagram). Ridge vents run along the ridge of the roof, and eave and soffit vents are located at the base of the roof. With this combination, the natural convection of the hot air in the attic powers the venting. In addition, because of the locations of the inlet and outlet vents, virtually the entire attic space is vented, reducing the likelihood of pockets of hot air.

Mechanical venting can provide adequate venting for the house, but is dependent on electricity. Other forms of venting, such as the ridge/soffit combination mentioned above, provide superior venting, but require modification of the roof to install. If you were already planning on installing a new roof, you should seriously think about a ridge/soffit combination.

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We have condensation water drops on the vents that blow air into our living room. We have central air and we live in Wellington, FL. What could cause this condensation?

Condensation occurs when air is cooled enough that it can't hold the moisture in it. It often occurs when an air conditioner is on but usually collects on the unit outside and drains or evaporates. The thermostat setting might be too low, the air conditioner might need a tune-up, or a dehumidifier may be required.

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Windows

I keep getting ads in the mail for companies offering to replace our windows with "energy-efficient" windows. How much can these save me?

For a typical house, windows can account for 10% to 30% of the heating and cooling bill. Upgrading from single-pane windows to energy-efficient windows can cut this in half or better, so savings of up to 15% of current bill are reasonable. Depending on where you live, this can amount to $50 to $100 per year. Spread over 20 years, this means $1,000 to $2,000. You can get a better estimate by running our Home Energy Adviser.

But the big thing to keep in mind is that many of these window replacement firms use simple double-pane windows; for just a little more money up front, you can save a lot of energy over the long haul by asking for windows with special low-e coatings and inert gases, such as argon or krypton, which fill the space between the panes of glass. Some manufacturers even offer 'superwindows' with one or two thin plastic films sandwiched between the panes of glass. These windows can reduce energy loss to one-half as much energy as standard double-pane glass, and one-fourth as much as single-pane glass. In cooling-dominated climates, use windows that reduce solar gains. For the most appropriate window in a givenclimate, purchase windows with the ENERGY STAR label.

Ask the salesperson to tell you the "U-value" of the windows they offer. This is sort of like the miles-per-gallon rating for new cars; an independent agency performs these ratings. In this case, lower is better: the best you can buy today have U-values of around 0.2, while a typical double-pane window is around 0.5.

Note: One thing to keep in mind is that replacing windows is often not justified solely on the basis of energy savings. The cost of replacing windows in existing housing is quite expensive the cost is typically not paid back for 20 to 30 years or more. However, replacing windows will make a substantial difference in the comfort of the home, which could well be worth the cost. Also, double-paned windows typically add to the value and saleability of the home if you put it on the market. In new construction, the labor costs are equivalent regardless of the quality of window installed, so buy the best you can afford.

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Over the winter, fog appeared between the panes of my double pane windows, but during the summer it went away. Why did this occur?

Fog, or condensate, on multiple pane windows is caused by moisture between the glass layers. When it is cold, the moisture condenses on the outer glass pane, very much like water beading up on the outside of a cold glass of water.

There are several reasons why the condensate might have disappeared. One is that the windows might be double-paned, but not sealed. These windows generally have a small air tube connecting the air space between the glazings to the outside. If this tube becomes completely or partially blocked, perhaps by snow or mud, condensation would build up during the colder months. In this case, the blockage could have cleared during the warmer weather. Check for the presence of an airtube in the windows and make sure it is unobstructed. If the double pane windows have been in place for a long time, it is very likely that this is the problem.

If you have sealed windows, like most modern double-pane windows, it is possible that the amount of moisture that leaked into the airspace is very small, small enough to remain in the air as water vapor when the air is warmer. If this is so, you can probably expect it to return next winter.

Another possibility is that the leakage is very large. Once the weather warmed up, the moisture equalized with the outside air, clearing up the fog. Generally, once the seal on a window has leaked, there isn't much you can do to repair it, and you will probably have to replace the window. In either case, check the warranty on the windows. Most sealed double-paned windows have some form of warranty against leakage. A lot of warranties have a limited life, but some are lifetime.

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Water Heating

Is there any rating for electric water heaters? I would be interested in knowing the ratings for brands.

Federal appliance standards require that all water heaters achieve a certain rating on a standardized scale. The rating for water heaters is called the Efficiency Factor (EF), based on the use of 64 gallons per day under standard test conditions. The federal appliance standards require the following EFs for electric water heaters:

Size Efficiency Factor (EF)
30 gallon 0.91
40 gallon 0.90
50 gallon 0.88
60 gallon 0.87

The most efficient electric water heaters have EFs around 0.94 to 0.96.

This Energy Factor can be converted into an estimate of annual consumption, for standard operating conditions. This estimate, in kWh/yr is the number you will see on the yellow Energy Guide sticker. There is a list of the most efficient water heaters, compiled by the American Council for an Energy Efficient Economy (ACEEE).

Here are some general trends in water heater efficiency:

  1. Larger tanks tend to be less efficient than smaller tanks, because they have more surface area through which to lose heat.
  2. Electric water heaters are more efficient than gas or propane heaters because the latter lose heat from the exhaust gases in the burner. As a result, some of the heat produced just goes up the chimney. However, because electricity tends to cost more than gas, water heating bills are usually higher with electric than gas.
  3. Heat pump water heaters are more efficient than electric resistance water heaters because they don't generate the heat used to heat the water; they just move heat from one place to another. Heat pump water heaters cost more to purchase than other types of water heaters.

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What is the average setting on an electric hot water heater?

Typically, water heaters have three temperature settings: high, medium and low. These settings correspond roughly, depending on the age and condition of the water heater, to about 160°F for high, 140°F for medium, and 120°F for low. Most people have the temperature set to medium, or around 140°F. If it is not already there, you should consider lowering the thermostat to 120°F, which will save you about 3 to 5% in water heating costs for each 10°F reduction. You might want to consider a timer for the water heater that turns it off when not in use, say between 10 or 11 pm to 6 am. This would also lower water heating costs by cutting down the amount of energy lost through the walls of the tank during the night.

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If the hot water heater is turned off during the day, won't it cost more because you then have to heat up the whole tank and wait minutes before taking a shower? Also, isn't it kind of an inconvenience?

No, water heater energy consumption increases with higher water temperatures, and water heaters use more energy to heat water up and keep it hot than they do to heat it up once, because heat is lost through the walls of the tank in proportion to the tank temperature. The same energy is required to heat up the water regardless of whether it is heating a little bit at a time, or all at once. Heat losses through the tank walls or pipes simply add to the cost. So, turning the water heater off for a few hours each day actually saves some energy. This strategy works best for electric water heaters, because they lose heat less rapidly than gas or oil water heaters.

If the water heater is off during the day, it would be an inconvenience if the occupant uses more hot water than is stored in the tank. Installing a timer that turns the water heater off or that lowers the temperature during the night generally poses no inconvenience at all. These timers can be set to turn the heater back on an hour or so before you get up in the morning.

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Computer

We're putting in a home office. Do computers and fax machines really use that much energy?

If you use a PC built before 1994, it can use around 200 W, and a laser printer can use around 100 W; if you leave this on 24 hours per day this can add up to over $200 a year. But many PCs, monitors and printers built since 1995 have "ENERGY STAR" capabilities, which save a lot of energy when you enable this feature.

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Should I leave my computer on all the time, or turn it off when not in use?

Only you can decide whether to leave a computer on, or turn it off. There are reasons for each strategy. The typical computer draws around 100 Watts, or 2.4 kWh/day. Multiply this by the electricity rate per kWh to come up with the cost per day. Leaving a typical computer on all the time would cost about 21¢/day (2.4 kWh * 8.6¢/kWh). This may not seem like much but it adds up to close to $75/year. If there is no particular reason to leave a computer on, that money would be needlessly spent.

There are reasons to leave a computer running 24 hours per day. One is if it is used as a web server, or to receive faxes 24 hrs/day. If these do not apply, then it makes sense to turn off the computer when it is not in use.

Don't worry about wear on the computer from turning it on and off repeatedly. This was once a problem in the early days of personal computers, but now the computer undergoes more wear from running constantly than from being turned off when not in use. If you do leave it on, try to have an ENERGY STAR unit. There are aftermarket devices to turn the computer after extended periods of inactivity.

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I have a Powermac 8500/180 and am wondering what I can do to lower its energy use. You mention that some new computers have ENERGY STAR compatibilities. My computer was made in 1996. Please help, my energy bill skyrocketed the month I plugged the computer in.

From the Apple menu, select Control Panels and then "Energy Saver". This lets you set the energy use feature—how quickly it turns the monitor off after the computer has been idle, and how quickly it allows the disk drive to spin down to a stop. Start by setting these to blank the screen after five minutes of inactivity, "Sleep" after 15 minutes, and "Shut Down" after one hour.

If you have been using a screen saver, you might reconsider. It's fun to look at, but you are paying for that entertainment.

The 8500 has a maximum power consumption of about 200 W, and the monitor an additional 100 W. (The *maximum* the 8500 box itself can draw is 200 W, if there are a lot of high-powered cards installed; usually it uses much less.) In "sleep" mode, it draws less (about 15 W).

With this information, you can figure out that the worst-case consumption should be something like 300 W x 24hr/day = 7,200 Whr/day, or 7.2 kWh. If the electricity is 10¢/kWh, this costs a maximum of 72¢/day, or $21/month.

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Do you really think my answering machine uses more electricity than my computer?

Surprising though it may seem, most answering machines use more energy than most computers. Here's how it breaks down:

  Answering Machine Computer
Energy Consumption 5 Watts 200 - 250 Watts
Typical Usage 8760 hrs (always on) 10.5 hrs/month or 126 hrs/yr
Annual Consumption 43.8 kWh/yr 25 to 32 kWh/yr

The equation to derive the annual consumption is:

Annual consumption = Energy Consumption (Watts) * 1 kWh per 1000 Watts * Usage per year

Obviously there are assumptions about typical usage and typical consumption. The numbers used in The Home Energy Saver are national average numbers, which may not accurately reflect the particular use and computer system. If the user works at home and uses the computer every day, the module will not portray the energy consumed accurately.

This type of assumption is present throughout the Home Energy Advisor for end-uses that do not typically result in a significant portion of household energy consumption. Simplifications like this one shorten the time required to enter inputs, without greatly reducing the accuracy of the overall estimates.

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Lighting

My utility company tried telling us to use more fluorescent lights to save energy, but I hate how fluorescent lights flicker when you turn them on and then make that annoying hum. And they make everything look sort of blue and cold. Isn't there anything better?

Yes, fluorescent lighting technology has significantly improved in recent years. One such technology is called "electronic ballasts." Unlike the older magnetic or transformer ballasts, electronic ballasts eliminate that annoying hum and flicker and allow the bulbs to emit light which is better quality. And instead of slowly getting brighter as they warm up, they turn on instantly.

Fluorescent bulbs are also available now that have better color. When purchasing bulbs there are two things to look for: the Color Rendering Index (CRI) and the Correlated Color Temperature (CCT). The CRI rates the ability of the bulb to render an object's true color when compared to sunlight. Look for lamps with a CRI of 80 or higher. The CCT refers to the color objects emit when heated to a certain temperature on the absolute temperature scale (Kelvin). The lower numbers correspond to reddish color and the higher to blue-white color. For color similar to incandescent lighting look for CCTs around 2700. Often, the warm, white fluorescent lamps are sold as "kitchen and bath" lamps.

Lamp CRI CCT
Incandescent 90-95 2700
Cool-White Fluorescent 62 4100
Warm-White Fluorescent 51 3000
Compact Fluorescent 82 2700
Halogen 95+ 2950

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Is it better to turn lights off when you leave the room? I heard somewhere that it uses more energy to turn lights off and on than to leave them running.

That used to be the case with fluorescent lights, but advances in technology, especially in ballasts, have resulted in lights that do not use appreciably more energy to start up. Turning fluorescent lights on and off does slightly shorten the lifetime, in hours, of the bulbs, but you will have to replace the bulbs less frequently if they are not running all day long. Incandescent lights do not require additional energy to start, in any event, so if you are leaving the room for more than a couple of seconds, you will save by turning the lights off, for both fluorescent and incandescent bulbs.

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