- ENERGY STAR reports that certified smart thermostats saved an average of about 8% on heating and cooling costs in field data.
- ENERGY STAR also notes heating and cooling make up almost half of a typical US home's energy bill.
- Savings are biggest for homes that held one temperature all day and night before.
- Heat pump owners should avoid deep setbacks that trigger expensive backup heat.
Where the savings come from
A thermostat does not make your furnace or air conditioner more efficient. It saves energy by running that equipment less. Every hour your home sits closer to the outdoor temperature, it loses or gains heat more slowly, so the system works less.
Smart thermostats do this in a few ways:
- Schedules and learning: they lower the heat or raise the cooling setpoint while you sleep or are out, and many build the schedule from your behavior.
- Occupancy and geofencing: sensors or your phone's location tell the thermostat when the house is empty.
- Remote control: you can fix a forgotten setting from your phone.
- Usage reports: monthly summaries show how long your system ran, which helps you spot problems.
The US Department of Energy has long estimated that turning your thermostat back 7–10°F for eight hours a day can save up to 10% a year on heating and cooling. A smart thermostat is simply a reliable way to make that happen without thinking about it.
What the evidence says
ENERGY STAR certifies smart thermostats based on actual field data from homes using them, not just lab tests. Its program found that the average home saved about 8% on heating and cooling, or around $50 a year at the time of that analysis. Because energy prices have risen since then, the dollar figure for many households today is likely to be higher.
That 8% is an average. Homes with a strict manual routine may see little extra benefit. Homes that kept the heat at 72°F around the clock may see much more.
Worked example: estimate your payback
First, estimate how much you spend on heating and cooling. ENERGY STAR notes that heating and cooling account for almost half of the typical US home's energy bill, more than $900 a year. Let us use $900.
Annual savings at 8%: $900 × 0.08 = $72 a year
Suppose the thermostat costs $150 and you install it yourself.
Simple payback: $150 ÷ $72 = about 2.1 years
If your utility offers a $50 rebate, the payback falls to $100 ÷ $72 = about 1.4 years. Here is how savings scale with your spending:
| Annual heating and cooling spend | 5% savings | 8% savings | 12% savings |
|---|---|---|---|
| $600 | $30 | $48 | $72 |
| $900 | $45 | $72 | $108 |
| $1,500 | $75 | $120 | $180 |
| $2,500 | $125 | $200 | $300 |
To estimate your own heating and cooling share, compare your highest winter or summer bills with your mildest months. The difference is roughly what you spend on climate control. Our appliance cost calculator can help with the arithmetic.
Smart thermostats and heat pumps
Heat pumps need different handling from furnaces. Most have electric resistance backup heat, which costs two to three times more per unit of heat than the heat pump itself. If you set the temperature back 8°F overnight, then ask for a fast recovery in the morning, many systems switch on that backup heat to catch up quickly. That can wipe out the savings.
To avoid this:
- Choose a thermostat that supports heat pumps and has a smart or adaptive recovery feature.
- Use modest setbacks of about 2–4°F rather than deep ones.
- Configure an auxiliary heat lockout temperature so backup heat runs only when it is truly cold outside.
- For variable-speed systems, check whether the manufacturer recommends its own communicating thermostat. ENERGY STAR notes this can be the better choice for very high-efficiency equipment.
Learn more in our heat pump guide.
Before you buy: compatibility and installation
Most smart thermostats need a constant power supply, usually through a "C-wire" (common wire) at the thermostat. Older homes often lack one. Some models include an adapter, and an HVAC technician can run a new wire. Check the manufacturer's compatibility tool with a photo of your current wiring before buying.
Turn off power to your heating and cooling system at the breaker or service switch before removing the old thermostat. If your thermostat runs on 120 or 240 volts, such as many electric baseboard heaters, you need a line-voltage model designed for that, and an electrician is the safer choice. Never connect a low-voltage smart thermostat to line-voltage wiring.
Wi-Fi reliability matters too. ENERGY STAR suggests keeping the thermostat within good range of your router or adding an extender.
Bonus value: utility programs
Many utilities offer rebates on certified smart thermostats or pay you to join demand response programs. In these programs, the utility may briefly adjust your thermostat by a few degrees during peak demand events, usually with an option to override. If you are on time-of-use rates, a smart thermostat can pre-cool or pre-heat before expensive hours. Check our incentives page for programs near you.
The verdict
For most households that do not already manage their thermostat carefully, a smart thermostat pays for itself within a few years and improves comfort. The bigger wins still come from fixing the house itself through insulation and air sealing. A thermostat controls your heating system; it cannot stop heat leaking out of the attic.
See ENERGY STAR's smart thermostat page for certified models and buying tips.
Frequently asked questions
Does turning the heat down at night really save energy?
Yes. A cooler home loses heat more slowly, so the energy saved overnight is greater than the energy used to warm back up. The exception is heat pumps that rely on backup resistance heat to recover, which is why modest setbacks work better for them.
Are smart thermostats better than programmable ones?
A programmable thermostat can save just as much if you program it well and keep it updated. Smart models help because many people never program the old kind, or override it and forget.
Can I install a smart thermostat myself?
Many people do if their system uses standard low-voltage wiring and has a C-wire. Turn off power first and follow the compatibility checker. Line-voltage systems call for an electrician.
Do smart thermostats work with radiators or boilers?
Many do, but compatibility varies by model and control setup. Check the manufacturer's compatibility tool, and consider room-by-room radiator controls for hydronic systems.
Run your own numbers
Plug your bill, prices and climate into our free appliance energy cost calculator — every assumption is editable.
This guide is general information, not financial, tax or engineering advice. Prices and incentives change — confirm with qualified local professionals and official program sources. See our methodology and disclosures.