What is the best temperature to set AC in summer?

The U.S. Department of Energy recommends 78°F when you're home, 85°F when away, and 82°F while sleeping. Every degree above 72°F saves roughly 3% on cooling costs. Most people find 74–76°F comfortable as a compromise between comfort and efficiency.

What temperature should I set my heat in winter?

DOE recommends 68°F when home and awake, 60°F when asleep or away. Each degree lower saves about 1% on heating costs. 68°F feels cool to some people — adjust based on your household, but try to stay above 60°F to prevent pipe freezing in cold climates.

Is it cheaper to leave AC at one temperature all day or adjust it?

Adjusting saves money. The myth that 'it costs more to cool down a warm house' is false — an AC cycling on from 82°F uses far less energy than holding 72°F all day. Smart or programmable thermostats automate this easily.

What temperature should I set AC to sleep?

Most sleep research suggests 65–68°F is optimal for sleep quality. The DOE recommends 82°F (efficiency), but comfort matters too. A ceiling fan on low allows you to sleep comfortably at 72–74°F without running AC harder.

What Temperature Should I Set My Thermostat?

The right thermostat setting balances comfort and cost — and the two don't have to be as far apart as you might think. Here's what the research says, plus practical adjustments for different households.

DOE Recommended Settings

The U.S. Department of Energy publishes specific guidance:

Summer (cooling): | Situation | Recommended Temp | |-----------|-----------------| | Home and awake | 78°F | | Away from home | 85°F | | Sleeping | 82°F |

Winter (heating): | Situation | Recommended Temp | |-----------|-----------------| | Home and awake | 68°F | | Sleeping | 60°F | | Away from home | 60°F |

These are efficiency-optimized settings. Most people find 78°F in summer slightly warm — especially during physical activity. 74–76°F is a common real-world compromise that still saves significantly compared to the 68–72°F that many households default to.

The Math: What Each Degree Actually Costs

For cooling: every degree you lower the thermostat below 78°F increases cooling energy use by approximately 3%. Setting your AC to 72°F instead of 78°F uses roughly 18% more energy — for the same outdoor conditions.

For heating: every degree you lower the thermostat saves about 1% on heating costs per 8 hours. Setting back from 68°F to 60°F overnight for 8 hours saves roughly 8% on that night's heating.

Over a full summer or winter, these percentages add up to real money on your utility bill.

Adjusting for Your Household

With young children or infants: The standard range is fine, but avoid extreme setbacks — large temperature swings can be harder for infants to adjust to. Keep sleeping temperatures between 68–72°F for newborns.

With elderly household members: Older adults are more sensitive to cold and heat. 72–74°F in summer and 70°F in winter is more comfortable and safer for many seniors.

With pets: Dogs and cats tolerate heat better than humans but can overheat. The ASPCA recommends keeping indoor temperatures above 80°F only for brief periods when pets are home alone. 78–80°F when away is acceptable for healthy adult pets; use 75°F or lower for flat-faced breeds (bulldogs, pugs) that overheat more easily.

The "Leave It Alone" Myth

Many people believe it's more efficient to leave the AC running at a constant temperature all day rather than letting the house warm up and then cooling it down. This is false.

A house at 85°F requires significantly less total energy to cool to 78°F once than a house that has been held at 72°F all day. The physics is simple: the larger the temperature difference between inside and outside, the faster heat flows into the house. A cooler house loses its cooling faster.

Smart thermostats handle this automatically — they pre-cool the house before you arrive based on your schedule, so you return to a comfortable home without having cooled it all day.

Smart Thermostat vs Programmable Thermostat

A programmable thermostat lets you set a schedule (workdays, weekends). It's a step up from manual adjustments but requires setup.

A smart thermostat learns your patterns, adjusts based on occupancy, and can be controlled remotely. The Nest and Ecobee routinely pay for themselves in energy savings within 1–2 years.

Recommended options:

Google Nest Learning Thermostat — self-learning, sleek, very easy to set up
Ecobee SmartThermostat Premium — room sensors, Alexa built-in, works well in larger homes
Honeywell Home RTH7560E Programmable — budget-friendly, no WiFi needed, simple 7-day programming

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Ceiling Fans: The Easy Multiplier

Ceiling fans don't change air temperature — they change how temperature feels through the wind-chill effect. A ceiling fan on low can make 78°F feel like 72°F.

Run ceiling fans counterclockwise (when viewed from below) in summer for a cooling downdraft. Switch to clockwise in winter to push warm ceiling air down.

This simple adjustment lets most people raise the AC setpoint by 4°F without noticing a comfort difference — which saves about 12% on cooling costs.

What Temperature Is Too Cold?

In winter, avoid setting the heat below 55°F in occupied homes in cold climates — water pipes can freeze in interior walls if temperatures drop too far. 60°F is the safe minimum for unoccupied periods when pipes are at risk.

For vacation or extended absence in winter, 55°F is generally considered the minimum safe temperature for homes with standard plumbing. Drain pipes if you'll be away for extended periods in very cold weather.