CO2 Smackdown, Step 5: Low-Cost Cooling

The Levine home in Southern California exemplifies elements of passive cooling, including a "rain curtain" (right) fed by a storm water collection system that cools downstairs air via evaporation and recirculates in a fountain. Slatted sun panels (left) can be closed during the day to reduce heat then opened when the sun has passed overhead. Credit: Jeremy Levine Design/Flickr
A quick look at your summer heating bill will confirm that cooling your home is expensive—in fact, according to the EPA AC accounts for 21% of annual home electricity consumption at an average cost of $239 year. Per household, that results in 1.5 tons of CO2 emissions from AC alone. But by following the steps outlined in this step of our year-long CO2 Smackdown series, you can save at least $494 and .95 tons of CO2 and even more if you upgrade your AC or replace with a ceiling fan.

What is our CO2 Smackdown? Read the overview.


1) Tell your A/C what to do: a programmable thermostat lets you save money by not cooling your house when you're not around to enjoy it. Set the temperature at 80°F when you know you'll be away and set it at least 2 degrees higher than you would normally—a shift from 72°F to 74°F in the summer will save 366 pounds of CO2/year and $28.56 on your annual energy bill.

2) Seal, weatherstrip and insulate your home to keep hot air out and cold air in. As recommended previously in our CO2 Smackdown series, weather stripping and talking doors, windows and any cracks or openings and walls will save about 225 pounds of CO2 and $17.71 from AC use in the summer.

It is also important to insulate around window air conditioners which can lose cool air to be outside particularly if the unit has extended plastic "wings" to fill in the window frame. Insulating kits for window air conditioners are available at hardware stores for approximately $10.

Remember to clean or check the conditioner filter once a month as any buildup will restrict airflow and make it less efficient.

3) Seal and wrap your ducts: the ductwork that conveys your cool air from the HVAC to the rest of your house may be leaking air at losing efficiency. This can result in a 10% "leaky duct fee" on your power bill. Get your ducts professionally sealed and have been insulated properly. If possible, have your ducts moved inside the conditioned space. You may save 305 pounds of CO2/year and $23.82 on your energy bill annually.

4) Windows: After weatherstripping your windows, consider adding low-emissive film to the panes to reduce solar gain. This will allow you to reduce the heat entering your home for a fraction of the cost of replacing your windows. If you decide to invest in new windows, seek out the lowest available U-factor, which measures how much heat can escape, and the lowest solar heat gain coeffiecient (SHGC), which measures how much heat from sunlight is transmitted through a window. A 30% of federal tax credit is available for windows with U-factors and SHGCs of 0.30 or less each. SHGC is most important in sunny climates and on the sunny side of your home.

5) Start cooling from the outside: awnings, shutters and overhangs will provide a good defense against the summer sun, but you may also use trees and tall bushes to beautify your view and reduce the sunlight entering your windows.

6) Close the blinds: shutting curtains, shades or blinds on the sunny side of the house can make a big difference particularly blinder venetian shades with highly reflective light colors can reduce heat build up in your home.

7) Let in fresh air: When it’s not too hot out, pull in cool air by cracking open lower story windows just one or 2 inches and place portable and window mounted fans and upstairs windows facing outward to remove the air that rises due to convection your home. This will create a stronger draft throughout the house that will keep the air cool without the use of AC.

8) Install ceiling fans: fans use 10% of the energy consumed by AC and can make a room feel 10° cooler. They are even relatively easy to install yourself, as shown in our DIY installation article. Replacing your AC with ceiling fan could save you up to $215 and 1.35 tons of CO2 annually.

10) Install an attic fan: whole house fans that remove hot air from throughout the house only provide substantial relief at night and in low humidity. A cheaper option is an attic fan which can save up to 10% on AC costs—that’s $24 and 300 pounds of CO2 annually.

11) Upgrade your AC: Whether central air or window-mounted AC, if your cooling system is several years old you can most likely save on your energy bill by upgrading to new, more efficient models. The most efficient models use inverter technology which also makes them very quiet. 30% tax credits are available for units 16 SEER and better. Depending on the age of your current unit, Energy Star-rated air conditioning could save you 10% to 30% of your cooling costs, or up to $71.52 and 916 lbs of CO2 annually.


For Federal tax incentives see the Tax Incentives Assistance Project for information about the limits on energy efficient home improvements. For a listing of state incentives, visit the Alliance to Save Energy. Be sure to check out the Department of Energy’s “5 Things You Should Know Before You Claim Your Energy Tax Credit,” which points out that installation costs for insulation costs cannot be claimed when determining your tax credit.

Depending on your income, you may qualify for free weatherization services through the Weatherization Assistance Program. This service is also available to renters.


Consider an evaporative cooler if you live in a dry, hot climate. Evaporative coolers (also known as "swamp coolers") draw outside the air over wet pads thereby cooling it. Although they only work in dry climates, evaporative coolers consume 75% less energy than conventional AC and can reduce indoor temperatures by almost 30°F. This could save you $179 and 1.15 tons of CO2 annually.


Do have any idea what a mobile home temperature can become by sitting all day in 110 degree heat without the air running? Or how long it will run to make up the difference? Think again. That is wasting energy.

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