Does Turning the AC Off While You're at Work Actually Save Money?
Yes. The US Department of Energy (DOE) says turning the thermostat back 7–10°F for 8 hours a day can save up to about 10% a year on heating and cooling. Switching the AC off is the far end of that same setback.
The DOE figure is for a daily routine: letting the house warm while you’re out, then bringing it back down. So the cool-down when you get home is part of that routine, not something added on top of it. What changes the answer for a particular house is humidity, who’s home during the day, and when your utility charges the most. Those are covered below, after the math.
Why this matters more on your electric bill than you’d think
The US Energy Information Administration (EIA) says air conditioning accounted for 19% of home electricity use in 2020. About 89% of US homes used AC that year, up from 57% in 1980. DOE’s Energy Saver 101: Home Cooling puts space cooling at just 6% of a household’s total energy, counting gas and other fuels. Home cooling mostly runs on electricity, though, so in summer it shows up on your power bill.
Work out your own savings
You need two numbers from your bills: your summer usage and your usage in a mild month with no heating or cooling.
Step 1: find your cooling kWh. As an example:
- July usage: 1,500 kWh
- April usage (no AC, no heat): 600 kWh
- Cooling ≈ 1,500 − 600 = 900 kWh
Step 2: price it. The US average residential rate is roughly 17–18¢ per kWh (EIA). At 17¢:
- 900 kWh × $0.17 = $153 of cooling that month
Step 3: apply the setback. DOE’s figure is “up to” about 10%:
- $153 × 0.10 = up to about $15 a month
- Over a four-month cooling season: 4 × $15 = up to about $60
Swap in your own kWh and the rate printed on your bill. Rates range from about 11¢ to over 40¢ by state, so the same habit is worth very different amounts in different places.
The other lever: the temperature you keep while you’re home
The workday setback is only half the bill. The Sacramento Municipal Utility District (SMUD) advises 78°F or higher in summer. It estimates around 5–10% savings on cooling costs for every 2 degrees you raise the setting. DOE adds that ceiling fans let you set the thermostat about 4°F higher with no loss of comfort.
Continuing the example, raising the home setting by 4°F with fans running is two 2-degree steps:
- Low end: 2 × 5% = about 10%, or $153 × 0.10 ≈ $15 a month
- High end: 2 × 10% = about 20%, or $153 × 0.20 ≈ $31 a month
That’s SMUD’s estimate for its own customers, so treat it as a ballpark. The point is that the setting you live with every evening can be worth as much as the setback while you’re away. Fans cool people, not rooms, DOE notes, so switch them off when you leave.
Off or setback? Match it to your house
| Your situation | Do this | Why |
|---|---|---|
| Dry climate, nobody home all day | Off, or a large setback | No one needs cooling and the air needs little drying |
| Humid climate, nobody home all day | Setback of 7–10°F, not off | The AC is also your dehumidifier |
| Pets, an infant, or a heat-sensitive person home (any climate or rate) | Keep it on at a moderate setting | Comfort and safety come before savings |
| Time-of-use rate with an evening peak | Set back during the day, cool down before the peak | Avoids running the AC at the highest price |
| Smart thermostat | Let it set back automatically | Geofencing knows when you leave |
Humid climates: the AC is also drying the air
DOE explains that an air conditioner’s cooling coils remove both heat and humidity, and that one reason AC makes you feel cooler is the drier air. Switch it off for a whole humid workday and nothing is pulling that moisture out. The EPA wants indoor humidity below 60%, ideally 30–50%, to limit mold.
A setback keeps the system cycling now and then, which keeps some drying going. If you’re unsure how your house behaves, a cheap hygrometer will show whether humidity climbs past 60% while you’re gone. If your basement already turns musty by August, see why a basement smells musty only in summer.
Time-of-use rates: when you cool down matters
On a time-of-use plan, the price per kWh depends on the hour. SMUD’s Time-of-Day rate, for example, makes 5 to 8 p.m. on weekdays the most expensive window. It specifically asks customers to avoid running the air conditioner alongside other big appliances then.
Picture getting home at 5:30 and cranking the AC down. The cool-down then runs at the peak price. Schedule the thermostat to start cooling earlier in the afternoon, so the work is done before 5. You still save on the empty hours, and the catch-up happens at the cheaper rate. Check your own utility’s peak hours, since they vary by plan.
Smart thermostats do the remembering
ENERGY STAR says certified smart thermostats can use geofencing (your phone’s location) to detect when you’ve left and set the system back. It estimates about $100 a year in savings for homes with high heating and cooling bills, or homes that sit empty much of the day. That’s exactly the household this question comes from. Our guide to thermostat settings for every season covers the winter side of the same schedule.
Before you blame the thermostat
If the setback isn’t moving your bill, the system itself may be wasting energy. DOE’s cooling guide says routinely replacing or cleaning the air filter can lower AC energy use by 5–15%. It also says air lost through ducts can account for about 30% of a cooling system’s energy. Leaky window and door trim lets hot air in all day too. Our caulking guide covers where those gaps hide. These no-cost habits for a lower electric bill stack on top of a setback rather than replacing it.
FAQ
Doesn’t the AC have to work harder later, cancelling the savings?
The cool-down does use energy, but DOE’s estimate of up to about 10% is for the routine of setting back and returning to normal every day. The house gains less heat while it’s warmer inside, and that’s where the savings come from. Timing matters more than the cool-down itself, especially on a time-of-use plan.
Is it safe to leave pets in the house with the AC off?
On a hot day, a closed house with the AC off can get uncomfortable fast, and that’s a risk for pets, babies, and anyone heat-sensitive. Use a moderate setback instead of switching it off when someone, human or animal, stays home.
What setting should I use while I’m home?
SMUD recommends 78°F or higher in summer, and DOE says ceiling fans let you raise the setting about 4°F without losing comfort. Start there and adjust in 2-degree steps.
Sources
- Programmable Thermostats (DOE Energy Saver) — a 7–10°F setback for 8 hours a day saves up to about 10% a year
- Energy Saver 101: Home Cooling (DOE) — fans allow about 4°F higher, AC removes humidity, space cooling 6% of household energy, filters 5–15%, ducts about 30%
- Electricity use in homes (EIA) and Average Price of Electricity (EIA) — AC at 19% of home electricity, 89% of homes with AC; the roughly 17–18¢ per kWh average
- Time-of-Day (5–8 p.m.) Rate (SMUD) — weekday 5–8 p.m. peak, 78°F or higher, about 5–10% per 2 degrees
- Smart Thermostats and Heat & Cool Efficiently (ENERGY STAR) — geofencing setbacks, about $100 a year for homes empty much of the day
- A Brief Guide to Mold, Moisture, and Your Home (EPA) — keep indoor humidity below 60%, ideally 30–50%
Written and reviewed by peter.bae for Hearth & Habit · Last reviewed October 11, 2026
Comments
Post a Comment