Energy consumption for home air conditioning accounts for more than 8% of all the electricity produced in the U.S. for all purposes at a cost to homeowners of over $15 billion. This translates to roughly 195 million tons of carbon dioxide, an average of almost 2 tons per year for homes with air conditioning. Follow these steps to lower the energy you use for cooling.
PLEASE NOTE: ACEEE does not rate or make recommendations regarding specific manufacturers or trade names. To get a better sense of the manufacturers that make the most efficient equipment, see STEP 3 for links to regularly updated product listings.
Before you consider upgrading your cooling equipment, the cheapest way to save money and energy from cooling is to reduce the need for mechanical air conditioning in the first place. This can be done in several ways (follow the links to learn more):
1. Insulate and tighten your house
Improving insulation and air sealing prevents heat from entering your house. Your highest priority should be to check insulation levels and air leaks between your living space and the attic.
2. Get rid of inefficient appliances
Inefficient appliances give off a lot of heat. Especially consider replacing or discarding old or auxiliary refrigerators; replace incandescent light bulbs with fluorescents or LEDs; and unplug electronic equipment when not in use.
3. Consider "cool" exterior finishes
When replacing your roof or painting your house, using light-colored or other "cool" roofing and siding products can reduce your peak cooling demand by 10-15%. There are a number of roofing products that can dramatically cut down on heat gain without blinding the neighbors. Start by looking for ENERGY STAR Reflective Roof Products .
4. Shade or improve windows
To keep high-angle summer sun out, consider horizontal trellises for your east and west-facing windows. Protect south-facing windows with deciduous trees or climbing foliage so you can take advantage of low-angle sun in the winter, when the leaves fall. New windows on those walls that get the most summer sun should have low-e glazings to block unwanted heat gain.
5. Cool with air movement and ventilation
Fan operation uses less energy than air conditioning and can be adequate for attaining desired comfort levels unless you live in a very humid climate.
Ceiling fans. Ceiling fans cool by creating a low-level “wind chill” effect throughout a room. As long as indoor humidity isn’t stifling, they can be quite effective. Just remember that a fan cools people — it doesn’t actually reduce room temperature — so turn it off when you leave the room. Look for ENERGY STAR rated ceiling fans .
House fans. Unless you live in a very humid climate, installing a large fan in your top-floor ceiling is a very effective way of cooling your whole house down without central AC. These fans suck air through the house, inducing a strong draft in rooms where windows are open as it pulls cooler, outdoor air inside. Check with your local home improvement retailer about available products and installation.
Because no two houses are alike, it is very difficult to advise what kind of new cooling system will be the most appropriate, efficient and cost-effective for your house. That is why the first step in replacing your system is finding a contractor who has experience in high-efficiency systems.
- Read our list of tips on choosing a contractor. Skilled air conditioner and heat pump technicians should always perform a cooling load calculation to determine proper sizing before making a recommendation.
- Have your contractor check all ducts before installing a new system. All ducts must be correctly examined to make sure they are sealed and insulated (where outside the building envelope) with supply and return systems balanced.
- If you do not already have a relationship with a contractor you can trust, find a contractor that employs technicians with North American Technician Excellence (NATE) training or ENERGY STAR experience. Listings are found at www.natex.org ((877) 420-NATE) or www.acca.org .
- If you are interested in installing a ground-source heat pump, the Geothermal Heat Pump Consortium lists contractors that specialize in this equipment.
Central AC and Heat Pumps
Central air conditioners and air source heat pumps are both widely used in the U.S. and are the best option for maintaining comfort in areas that experience high humidity. Heat pumps can be used very effectively both for heating and cooling in southeastern states. Both central AC and air source heat pumps are rated according to seasonal energy efficiency ratio (SEER). This is the cooling output divided by the power input for a hypothetical average U.S. climate. The higher the SEER, the more efficient the air conditioner. To get the best performance and highest efficiency possible from your new system, consider the following:
- ACEEE recommends SEER of at least 14.5 (15.0 for hot climates)
In all climates, ACEEE recommends consumers purchase new cooling equipment at the ENERGY STAR level. If you live in a very hot-humid climate, consider the advanced efficiency levels as defined by the Consortium for Energy Efficiency (CEE) . Your utility may offer incentives for equipment at these levels. Air conditioners and heat pumps meeting these performance criteria can be found by running a search in the ARI/CEE HVAC Directory.
- ACEEE recommends EER of at least 12.0
This ensures the unit is efficient throughout the year and when it is needed most (on the hottest days). If you live in a hot-dry climate, ACEEE recommends a high SEER (15) but a high EER is even more important: select the highest EER available. Better yet, consider an evaporative cooler instead.
Air Source Heat Pump
Ground Source Heat Pump
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How much money can I expect to save?
That depends on the price of electricity. You can compare the cost of running a new air conditioner to the cost of running your existing unit using the ENERGY STAR savings calculator. Just enter the price you pay for fuel or electricity from your utility bill. The ENERGY STAR savings calculators are downloadable Excel files; click to download the calculator you would like to use: central air conditioner or heat pump.
- Make sure indoor and outdoor units match
The refrigerant controls for new condenser units are incompatible with most pre-2006 indoor units. Installing a new outdoor unit without replacing the indoor unit is likely to result in low efficiency, and may lead to premature failure of the new compressor—the most important component. Ask your contractor or check the CEE Directory of ARI Verified Equipment to make sure that the combination of condenser and indoor unit your contractor has proposed meet the efficiency levels recommended by the Consortium for Energy Efficiency.
- High electrical efficiency
Ask your contractor about a variable speed air handler, which will improve comfort and efficiency and allow continuous air filtering at minimum energy cost. Never use continuous ventilation when the air conditioner is in use, because it will degrade humidity control.
- Specify R-410 Refrigerant
The refrigerant of an air conditioner is essential for operation. For decades residential air conditioners have used Freon (or R-22). Because R-22 released into the atmosphere causes long-term damage, R-22 will not be allowed in new equipment starting in 2010, but will still be available for repairs.
Evaporative coolers, sometimes called swamp coolers, are less common than refrigerated air conditioners, but they are a practical alternative in very dry areas, such as the Southwest. They work by pulling fresh outside air through moist pads where the air is cooled by evaporation.
You can get a direct evaporative cooler, which adds moisture to a house (could be considered a benefit in very dry climates), or an indirect cooler, which does not. For evaporative coolers to do their job, they must be the right size. The cooling capacity of an evaporative cooler is measured not in the amount of heat it can remove (Btu), but in the fan pressure required to circulate the cool air throughout the house, in cubic feet per minute (cfm). A good rule is to figure the cubic square footage of your house and divide by 2. For example, a 1,500 square foot house with 8 foot-high ceilings would require a 6,000 cfm cooler.
What if I want to get rid of my room air conditioners?
You have three options:
Room air conditioners are rated only by EER, which is cooling output divided by power consumption. The higher the EER, the more efficient the air conditioner. Federal minimum efficiency standards for room air conditioners were revised in 2011 with new standards set to take effect in 2014; ENERGY STAR requirements exceed the current federal standards by 10% or more. Room air conditioners are sized to cool just one room, so a number of them may be required for a whole house. Individual units will cost less to buy than central systems.
- ACEEE recommends an EER of at least 11.0. Check the ENERGY STAR list to find qualified products.
- It is critical that your window unit is properly sized.
ENERGY STAR provides a chart to help find the cooling capacity (in Btus) appropriate for your room. Too much capacity and the unit will cycle on and off too often, wasting energy. Too low and the unit will not cool well and will overdry the air. While the ENERGY STAR chart is a good place to start, note that square footage is not the only factor governing cooling capacity. As an example, if your room has a lot of windows exposed to summer sun, has ceilings higher than 8 feet, or is located directly under the attic, your cooling load might be one or two Btu classes HIGHER than the chart suggests.
Mini-split systems can be an attractive retrofit option for room additions and for houses using hydronic heat. Like conventional central air conditioners, mini splits use an outside compressor/condenser and indoor air handling units. The difference is that each room or zone to be cooled has its own air handler. Each indoor unit is connected to the outdoor unit via a conduit carrying the power, refrigerant and condensate lines.
The primary advantage is that, by providing dedicated units to each space, it is easier to meet the varying comfort needs of different rooms. By avoiding the use of ductwork, mini-splits also avoid energy losses associated with central forced-air systems.
The primary disadvantage of mini-splits is cost. They can cost 30% more than a typical central air conditioner of the same size. But, when considering the cost and energy losses associated with installing new central ductwork, buying a ductless mini-split may not be such a bad deal, especially considering the long-term energy savings. Talk with your contractor about what option would be most cost-effective for you.
The compressor units of most air conditioners have an average lifetime of only 10 to 12 years. By carefully following proper maintenance procedures, a quality model may hold up twenty years, but don’t expect the kind of lifetime you get with boilers and furnaces.
1. Reduce excessive use:
- Use air conditioning only when ventilation is inadequate.
- Set the temperature up when leaving the house.
- Always keep all doors and windows closed when operating an air conditioner.
- Don’t cool unoccupied rooms (but don’t shut off too many registers either, or it will put pressure on the system).
- Minimize indoor humidity by running hot-water appliances in the evening and by showering with the exhaust fan on.
- If your room air conditioner has an outside air option, use it sparingly.
2. Increase your comfort range by using fans.
With a ceiling fan, you will probably be comfortable with the thermostat set at about 78°F. Each degree you are able to raise the thermostat, you will save 3–5% on air conditioning costs.
3. Clean the air filters on room air conditioners monthly.
The filter in a central air conditioner should never be allowed to get dirty enough to impede air flow, as this could cause damage to the unit. The condenser should be cleaned by a professional every other year, or even yearly in dusty locations. Filters in Room AC units can simply be removed (typically located behind the air inlet grill) and rinsed to remove trapped dust. Many modern units have an indicator alerting you to when the filter needs to be cleaned. Otherwise, it is a good idea to check the filter every couple of months during the summer.
4. Hire a professional technician to inspect, clean, and tune your system every 2-3 years.
- During service of your unit, its refrigerant may need recharging. This correction can improve system efficiency by 20%.
- The technician should measure airflow over the indoor coil. Correcting airflow rates can improve efficiency another 5–10%.
- Regardless of how well tuned it is, the system will not operate efficiently if the duct system is in poor condition. Proper sealing and insulation can reduce cooling energy use by 10–15%.