Energy Guide
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Cooling costs 40-60% of most summer electricity bills. These strategies can reduce that cost by 15-30% without a noticeable comfort difference -- and many cost nothing to implement.
Free Thermostat Strategies
- Set it higher than you think. The US DOE recommends 78 degrees F when home, 85 degrees when away, and 82 degrees when sleeping. Each degree higher saves approximately 3% on cooling costs.
- Use schedules aggressively. Program the thermostat to let the home warm up during hours it is unoccupied. Even 3-4 hours of reduced cooling during work hours saves measurably over a season.
- Avoid the "blast it cooler" mistake. Setting the thermostat to 65 degrees F does not cool the home faster than setting it to 72 degrees F -- it just runs longer and overshoots. Set the actual target temperature.
- Use ceiling fans in occupied rooms. Running a ceiling fan counterclockwise in summer allows you to raise the thermostat setpoint by 4 degrees F without a comfort difference. Turn fans off when leaving the room -- fans cool people, not rooms.
Maintenance That Improves Efficiency
- Replace the air filter on schedule. A clogged filter increases energy use by 5-15% and stresses the compressor. Check monthly; replace every 1-3 months.
- Clean the condenser coil. Gently rinse the outdoor coil with a garden hose from the inside out each spring. A dirty condenser coil can increase energy use by 10-30%.
- Clean or clear the evaporator coil. A dirty indoor coil reduces cooling capacity. This requires a technician unless you are experienced -- but it is part of an annual tune-up.
- Check for duct leaks. Leaky ductwork in unconditioned spaces (attic, crawlspace) can waste 20-30% of your cooling. A duct test and sealing is a high-ROI investment in homes with accessible ductwork.
Home Improvements With Real ROI
- Add attic insulation. Heat radiated from a hot attic is a major cooling load. Adding insulation to R-38 or R-49 in hot climates is one of the highest-ROI energy upgrades available.
- Window treatments. Blackout curtains or cellular shades on south and west windows reduce solar heat gain by 30-40%.
- Weatherstripping and air sealing. Gaps around doors, windows, and penetrations allow cooled air to escape and hot air to enter. Air sealing typically costs $200-$500 and can reduce cooling costs by 10-15%.
Frequently Asked Questions
- What is the most effective way to reduce AC energy costs in summer?
- The highest-impact, lowest-cost strategies: use a programmable thermostat to raise setpoints when the home is unoccupied, keep the air filter clean, use ceiling fans in occupied rooms (allowing a 4-degree setpoint increase), and close blinds on south and west windows during afternoon heat. These together can reduce cooling costs by 15-25%.
- What temperature should I set my thermostat to in summer?
- The DOE recommends 78 degrees F when home, 85 degrees when away, and 82 degrees when sleeping. Each degree you raise the setpoint reduces cooling costs by approximately 3%. If 78 feels too warm, try 76 and use ceiling fans -- the air movement allows a higher setpoint without discomfort.
- How much can I save by cleaning my AC unit?
- A clean condenser coil can reduce cooling energy use by 10-30% compared to a dirty one. Regular filter replacement saves 5-15%. Annual professional maintenance (including coil cleaning and refrigerant check) typically pays for itself in energy savings plus prevention of more expensive breakdowns.
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