Smart thermostats: what they save and what they do not
ENERGY STAR says a smart thermostat must cut heating run time by at least 8% and cooling run time by at least 10%, measured across hundreds of real homes. Those are floors on equipment run time, not promises about your bill.
What the label means
A smart thermostat, in ENERGY STAR's words, is a Wi-Fi enabled device that automatically adjusts heating and cooling settings. To earn the label, makers use EPA-provided software to analyze a year of data from hundreds of their customers' homes and compute national savings metrics. We read the criteria page on 2 October 2026. The specification took effect on January 1, 2017.
ENERGY STAR sets two kinds of tests. One is a floor on the weighted national average. The other is a floor on the 20th percentile, which means 4 out of 5 homes in the sample saved at least that much. The table below shows all four numbers.
| Run time reduction | Weighted national average, lower 95% limit | 20th percentile, weighted national average |
|---|---|---|
| Heating | 8% or more | 4% or more |
| Cooling | 10% or more | 5% or more |
ENERGY STAR, Smart Thermostats Key Product Criteria, Table 2, retrieved 2026-10-02.
Run time is not dollars
The criteria measure how long the furnace or air conditioner runs. A bill depends on that run time, on the fuel, and on the price. ENERGY STAR gives no dollar saving per thermostat on the pages we read, so we give no figure. It does say that for the average American household almost half of the annual energy bill goes to heating and cooling, more than $900 a year. That is the pool a thermostat works on, and it is the same figure whatever state you live in, so treat it as a national average.
A gas furnace saving shows up on the gas bill, not the electric one. This site covers electricity. If you heat with gas, a smart thermostat helps your gas bill and your air conditioner's electricity use, but our price data covers only the second.
Where the pool is bigger
A thermostat has more to manage where winters or summers are long. Degree days measure that. North Dakota has the most heating degree days in the 1991-2020 normals, 9,619. Florida has the most cooling degree days, 3,191. Of the 48 states with data, 44 have more heating than cooling degree days in the normal year and 4 have more cooling.
9 states have a smaller side that is at least half the larger side, so a thermostat has work in both seasons there.
United States, Heating degree days, 1991-2020 normal, ten states: EIA retail sales.
CSV| State | Heating degree days, 1991-2020 normal | Cooling degree days, 1991-2020 normal | Larger side | Home price 2025, cents per kWh | Utilities offering home time-of-use |
|---|---|---|---|---|---|
| Minnesota | 9,035 | 422 | Heating | 15.82 | 21 |
| North Dakota | 9,619 | 423 | Heating | 11.81 | 5 |
| Massachusetts | 6,635 | 383 | Heating | 30.48 | 1 |
| New York | 6,495 | 486 | Heating | 26.39 | 3 |
| Illinois | 6,437 | 841 | Heating | 17.69 | 7 |
| Washington | 5,939 | 131 | Heating | 13.11 | 4 |
| Texas | 2,035 | 2,648 | Cooling | 15.47 | 14 |
| Florida | 774 | 3,191 | Cooling | 15.24 | 11 |
| Arizona | 2,207 | 2,707 | Cooling | 15.32 | 10 |
| Louisiana | 1,786 | 2,557 | Cooling | 12.57 | 2 |
Source: NOAA NCEI nClimDiv statewide degree days (base 65°F), files dated 2026-09-04; EIA retail sales 2025; EIA-861 2024 Dynamic_Pricing. Ten states shown, all {len(ks)} with 2025 and normal degree days in the CSV (Hawaii and DC: no data). Retrieved 2026-10-02. CSV, 48 rows.
Check your own saving
Weather moves your bill in both directions, so compare like with like. In 2025, 48 of the 48 states had fewer heating degree days than their 1991-2020 normal: Ohio had 5% lower heating degree days than normal and Arizona had 29% lower. A home that installed a thermostat before a mild winter could credit the device with a saving that was the weather.
| State | Heating degree days 2025 | 1991-2020 normal | 2025 against normal |
|---|---|---|---|
| Ohio | 5,756 | 6,062 | 5% lower |
| West Virginia | 5,055 | 5,359 | 6% lower |
| Indiana | 5,587 | 5,941 | 6% lower |
| Pennsylvania | 5,729 | 6,110 | 6% lower |
| Wisconsin | 7,348 | 7,934 | 7% lower |
| Arizona | 1,560 | 2,207 | 29% lower |
| Texas | 1,519 | 2,035 | 25% lower |
| Nevada | 2,920 | 3,762 | 22% lower |
| California | 2,525 | 3,253 | 22% lower |
| Florida | 617 | 774 | 20% lower |
Source: NOAA NCEI nClimDiv statewide heating degree days, base 65°F. Five states closest to their normal (or above it), then the five with the largest fall. Retrieved 2026-10-02. CSV, 48 rows.
A fair test: pick the same months a year apart. Note the kWh used each month, then look up that month's degree days. If degree days rose and your kWh fell, the thermostat likely helped. If degree days fell and your kWh fell by the same percent, the weather did the work. This site shows state totals only, so use the monthly degree days on NOAA's pages for your own state.
Buying notes from the ENERGY STAR page
ENERGY STAR lists these buying tips. Make sure the thermostat is compatible with your heating and cooling system. For very high efficiency equipment, such as an air conditioner rated 20 SEER or higher, you may want a controller from the same company. If the thermostat uses Wi-Fi, keep it reasonably close to the router.
ENERGY STAR also requires the device to work as a basic thermostat without a connection, to let you set a schedule, and to keep network standby power at 3.0 W or less on average. Its temperature accuracy must be within 2.0 degrees Fahrenheit either way. Those are the limits you can check on a spec sheet.
Utility programs
ENERGY STAR says certified smart thermostats are designed to work with programs some local utilities offer, and that the thermostat can work with utility programs while you keep the ability to override. In the EIA-861 2024 file, 358 utilities in 49 states and DC say they offer a residential time-of-use rate, and 15,832,411 home customers are enrolled in dynamic pricing programs of all kinds. We do not know how many of them use a thermostat. We also have no data on which utilities pay for thermostats: no data.
Ask your utility or look at the ENERGY STAR rebate finder before you buy. A rebate changes the math more than any run-time percentage does.
What this page does not claim
We do not claim a percent saving on your bill. ENERGY STAR's numbers are run time and the sample is homes of the companies that apply. They are not a sample of all homes. We have no data on thermostat prices, on how many homes already have one, or on savings in homes with electric baseboard heat or heat pumps. ENERGY STAR says it requires makers to report the use of electric resistance heat in heat pump homes but sets no limit.
See the seasonal bill guide, the heat pump versus gas guide, smart meters and time-of-use by state, heating cost by state and the glossary. Sources are on the data sources page.
Key facts and where they come from
| Fact | Value | Source | Date |
|---|---|---|---|
| Heating run time cut, weighted national average, lower 95% limit | 8% or more | ENERGY STAR Smart Thermostats Key Product Criteria, Table 2 | retrieved 2026-10-02 |
| Heating, weighted national average of 20th percentiles | 4% or more | ENERGY STAR Key Product Criteria, Table 2 | retrieved 2026-10-02 |
| Cooling run time cut, weighted national average, lower 95% limit | 10% or more | ENERGY STAR Key Product Criteria, Table 2 | retrieved 2026-10-02 |
| Cooling, weighted national average of 20th percentiles | 5% or more | ENERGY STAR Key Product Criteria, Table 2 | retrieved 2026-10-02 |
| Network standby power, average | 3.0 W or less | ENERGY STAR Key Product Criteria, Table 1 | retrieved 2026-10-02 |
| Static temperature accuracy | Within 2.0 degrees F | ENERGY STAR Key Product Criteria, Table 1 | retrieved 2026-10-02 |
| Average household heating and cooling spend | More than $900 a year (almost half the energy bill) | ENERGY STAR Smart Thermostats page | retrieved 2026-10-02 |
| Specification effective date | January 1, 2017 | ENERGY STAR Smart Thermostats page | retrieved 2026-10-02 |
| States with degree-day data | 48 | NOAA NCEI nClimDiv | files dated 2026-09-04 |
| Most heating degree days: North Dakota | 9,619 | NOAA NCEI nClimDiv | 1991-2020 normal |
| Most cooling degree days: Florida | 3,191 | NOAA NCEI nClimDiv | 1991-2020 normal |
| Utilities offering a residential time-of-use rate | 358 in 49 states and DC | EIA-861 2024 Dynamic_Pricing | 2024 data |
| Home customers in dynamic pricing programs | 15,832,411 | EIA-861 2024 Dynamic_Pricing | 2024 data |
Keep reading
Questions
How much will a smart thermostat save me?
ENERGY STAR does not give a dollar figure on the pages we read. It requires certified models to cut heating run time by at least 8% and cooling run time by at least 10% (national average, lower 95% limit).
What is the 20th percentile test?
ENERGY STAR says it means 4 out of 5 homes in the sample saved at least that much. The floors are 4% for heating run time and 5% for cooling.
Is the saving the same in every state?
No. Normal heating degree days run from 774 in Florida to 9,619 in North Dakota, so the hours a thermostat can manage differ a lot.
Does a smart thermostat lower my electric bill if I heat with gas?
It lowers the gas bill and your air conditioner's run time. This site has only electricity prices, so it cannot give the gas dollars.
What does ENERGY STAR require of the device itself?
A basic thermostat mode without a connection, a schedule, feedback on energy use, accuracy within 2.0 degrees F and network standby power of 3.0 W or less on average.
How do I test my own saving?
Compare the same months a year apart and adjust for weather. In 2025, Arizona had 29% lower heating degree days than its normal, enough to fake or hide a small saving.
Do utilities offer thermostat programs?
ENERGY STAR says certified models are designed for them. In EIA-861 2024, 358 utilities report a residential time-of-use rate. We have no list of thermostat rebates: no data.
What should I check before buying?
Compatibility with your heating and cooling system, Wi-Fi range near the router, and any utility rebate. ENERGY STAR lists the first two in its buying tips.
Space heaters
A thermostat does not control a plug-in heater in another room. How a room heater changes the bill.