Do Smart Thermostats Actually Save Money? Real Numbers for 2026

ENERGY STAR certifies smart thermostats against a hard quantitative floor. The Smart Thermostats Key Product Criteria require a manufacturer to demonstrate, using EPA-provided software against a year of data from hundreds of installed homes, that the lower 95% confidence limit of national savings reaches at least 8% for heating run-time and at least 10% for cooling run-time. Lower 95% confidence limit is statistician-speak for "take the average and haircut it for the chance the sample happened to be lucky." The actual mean is higher than the floor for every certified product. Nest, Ecobee, Honeywell, Sensi, and a few dozen smaller brands all clear this bar.

The number applies to HVAC run-time, not your total electricity bill. If the equipment ran 10% less, you paid 10% less to run it. Whether that's a meaningful dollar depends entirely on how much your equipment was running in the first place.

The EIA reports an April 2026 U.S. residential average of about 18.05¢/kWh. Run that rate against the kind of HVAC electricity spending real households see, and the 8% to 10% certification floor produces a fairly wide range.

Small home, gas heat, modest central AC: roughly $40 to $80 a year. Cooling is the only electric HVAC load the thermostat controls. A 2,500 to 4,500 kWh summer cooling baseline at a 10% reduction works out to $45 to $81 at 18.05¢. Smaller AC loads than that drop the savings into rounding-error territory.

Average household with central AC and electric supplemental heat:$120 to $160 a year. This is the modal U.S. case. The EIA puts HVAC at roughly 46% of residential energy use, and for an all-electric or mostly-electric household running about 8,000 to 9,000 kWh a year on conditioning, a 10% reduction is 800 to 900 kWh. At 18.05¢/kWh that's $144 to $162.

Large home, heat pump, cold climate: $180 to $260 a year. Heat pumps work harder for longer in cold regions and pull more electricity per hour than central AC. A 2,400-square-foot home in Maine or Minnesota can spend $2,000 to $2,600 a year just on heating and cooling electricity, and a 9% blended run-time reduction across both seasons clears $200 in nearly every case.

Hold the HVAC reduction constant at about 880 kWh a year, which is the implied saving for the average central-AC household above. The dollar value of that 880 kWh swings by where you pay your bill.

Louisiana (~11.5¢/kWh): about $101 a year. Texas (~14.5¢/kWh): about $128. U.S. average (18.05¢/kWh): about $159. New York (~22.85¢/kWh): about $201. California (~31.2¢/kWh): about $275. Hawaii (~41¢/kWh): about $361. The swing from Louisiana to Hawaii is 3.6x on identical equipment behavior. High-rate states benefit more from any HVAC reduction because the absolute dollars are larger. The math is in the rate, not the thermostat. See current rates by state for your own number.

The DOE Energy Saver Programmable Thermostats page states that pushing the thermostat back 7-10°F for 8 hours a day can save up to 10% annually on heating and cooling. The smart thermostat's headline number is anchored to the same physics. The implication, often missed in vendor copy, is that if you already do this manually, the smart thermostat is replacing behavior that was already saving you money.

For a household that already sets back 6-8°F overnight and during the workday, the upgrade to a learning thermostat is typically 2% to 3% on top of what manual discipline was capturing, not the full 8% to 10%. That's $30 to $50 a year for the average household instead of $120 to $160. Worth the device if the device pays for itself in three or four years, less obvious if it doesn't.

For a household that runs a constant 72°F year-round with no setbacks ever, the upgrade is closer to the full 10% because the equipment is running far more than it needs to. The smart thermostat's value scales with the gap between current behavior and the ideal schedule.

Hardware is the only real upfront cost for most homeowners doing the install themselves. Holding savings flat at the average central-AC household number, $160 a year:

Google Nest Learning Thermostat (4th gen): roughly $280 retail. Payback about 21 months. The learning algorithm builds a schedule from the first week of use without any programming work from the homeowner.

Google Nest Thermostat (4th gen, non-Learning): roughly $130-150. Payback under 12 months. Fewer features, same 8% and 10% certification floor.

Honeywell Home T9: $160-190. Payback 12-14 months. Ships with remote room sensors so the thermostat can balance temperature across a multi-story house instead of optimizing for one hallway reading.

Ecobee Smart Thermostat Premium: $230-250 retail. Payback 17-19 months. The premium model adds air quality monitoring and a built-in occupancy sensor that the entry-level Ecobee lacks.

Honeywell T5 budget programmable Wi-Fi:$80-100. Not ENERGY STAR certified at the smart-thermostat level, so the 8-10% number doesn't formally apply. Real-world savings from a programmable Wi-Fi model with manual schedule are typically 5% to 7% if you actually program it. Payback under 10 months because the hardware is so cheap.

High-rate states compress every payback period. The same Ecobee in California saves $275 a year and pays back in 11 months instead of 19. In Hawaii it's 8 months.

Heat pumps with aggressive setbacks can cost the homeowner money. When indoor temperature drops far enough below the setpoint, most heat pump systems engage electric resistance auxiliary heat to recover quickly. Resistance heat runs at roughly one-third the efficiency of normal heat pump operation. A 6°F overnight setback in a cold-climate heat pump home can trigger 30 to 60 minutes of resistance heat on the wake-up call, and the recovery cost frequently exceeds the overnight savings.

The ENERGY STAR criteria require certified smart thermostats to report electric resistance heat use for heat pumps, and the better algorithms throttle setbacks to avoid triggering it. A programmable thermostat with no heat-pump awareness will not. If your home runs a heat pump and you want aggressive setbacks, the smart thermostat with heat-pump intelligence is the better tool. A $40 programmable thermostat is the wrong tool. See heat pump running cost for the underlying numbers.

A smart thermostat draws 1 to 6 watts continuously to keep Wi-Fi alive and the display lit. The RunWatts smart thermostat calculator defaults to 3 watts, which at 8,760 hours a year is 26 kWh, or about $4.74 a year at the U.S. average rate. That's rounding error compared to the HVAC reduction it controls. The Nest Learning, Ecobee Premium, and Honeywell T9 all sit in this 2-3 watt range. The device's own draw never approaches a dollar a month even on Hawaii's 41¢ rate.

Smart thermostats don't save money. The schedule they enforce saves money. The 8% and 10% EPA certification numbers reflect what happens when an average household stops running HVAC at a constant setpoint and starts running it on a schedule that matches occupancy. A $30 mechanical programmable thermostat installed correctly and used consistently saves a household the same money as a $250 Nest Learning Thermostat. The smart thermostat's advantage is that it enforces the schedule without homeowner discipline. The programmable's disadvantage is that most households never actually program them.

If you've already automated your HVAC schedule and your bill is climbing anyway, the savings lever isn't the thermostat. It's equipment efficiency, building envelope, or rate plan. The summer bill checklist and why is my electric bill so high walk through the levers in order of dollar impact.

RunWatts publishes a calculator for smart thermostats and matched calculators for the equipment they control: central AC, heat pumps, and electric furnaces. Plug in the wattage of whatever you actually run, multiply by typical seasonal hours at your state rate, and apply the 8% or 10% reduction to the result. That gives the real ceiling for what a smart thermostat could save you, before any judgment about whether the device makes sense for your house.