Sometimes, under specific conditions, with a house that was wasting energy before you started. Not the flat 20% every manufacturer prints on the box. The independent field studies that measured real houses put the number closer to half that, and roughly a third of homes that install one save close to nothing.
Quick decoder
- Measured field savings from real houses: roughly 9-10% on heating and cooling energy, not 20%
- One large Oregon billing study found homes only banked 56% of the savings programs assumed they’d get
- 7 of 22 homes in a Florida field study saved nothing at all after installing a Nest
- Only 10.3% of US homes have a smart/internet-connected thermostat, per the most recent government survey
- The thermostat itself barely uses any power – the savings argument is about your HVAC system, not the gadget
The vendor claim vs. what got measured
“Save up to 20%” is the number every smart thermostat box, ad, and Amazon listing leads with. It is also, by the account of the people who study this for a living, a number nobody has verified. A 2016 paper co-authored by an EPA program lead and a Lawrence Berkeley National Lab researcher put it bluntly: “Thermostat vendors claim savings of up to 20%; however, there is no accepted procedure to evaluate the effectiveness of these strategies” (ACEEE, 2016). That is not a rival company sniping. That is the government body that runs the ENERGY STAR program saying the marketing math doesn’t have a receipt.
Check with real houses and real utility bills instead of a lab model, and the number collapses. The Florida Solar Energy Center ran a long-term field study of Nest and Lyric thermostats in actual occupied homes and weather-normalized the results. Average measured savings across 22 usable Nest installations: 9.3% on cooling, 9.5% on heating. Less than half the marketing number, and that’s the average, not the floor – 7 of the 22 homes had negative savings, meaning they used more energy after installing the thermostat than before.
And it’s not a fluke from one small study, either. Energy Trust of Oregon ran a billing analysis across 13,762 gas-heated homes from 2019-2023 – a genuinely large sample – and found homes saved an average of 22 therms a year against a program-assumed 39 therms. That’s a 56% realization rate: real houses banked a bit over half of what the utility program expected them to save (Energy Trust of Oregon, Nov 2025). Nest and ecobee performed about the same in that study – no meaningful brand difference, so this isn’t a “buy the better app” problem.
An Illinois utility ran into the same gap from a different angle. ComEd’s rebate program had assumed an 8% cooling-energy savings figure in the state’s technical reference manual. When Navigant went and measured what happened in real houses, it found 2% – and recommended the state cut its assumption to match. The state didn’t cut it, for what it’s worth, so if you see “8% verified savings” attached to an Illinois utility program, that’s the assumption, not the measurement.
Why the savings swing so hard between houses
The 7-of-22-homes-saved-nothing result isn’t random noise, it has a specific cause. The Florida researchers traced the negative-savings homes to two groups: houses where the old programmable thermostat was already set up properly, and houses where someone was already manually managing the temperature well. A smart thermostat can’t improve on a schedule that was already good. It can only fix a bad one.
Here’s the part that should worry anyone buying one purely for the savings pitch: most people never turn on the thing that produces the savings. EIA’s national household survey found that while 53% of US homes have a programmable or smart thermostat, only about a third of those owners use the programmable or automated scheduling features to control temperature. Two out of three people who own the hardware are running it in manual mode, which means they paid for a feature they aren’t using.
Put those two facts together and the verdict writes itself. A smart thermostat saves you money if your house currently has bad temperature habits (an unset schedule, a “just leave it at 72 all day” setup, forgetting to adjust before vacation) and the automation gets turned on and used. It saves you nothing if either of those isn’t true.
How many people have one
Every “smart thermostat adoption” headline you’ve seen probably cites something in the 40-50% range. That number is accurate, but it’s measuring the wrong category. The government’s 2020 Residential Energy Consumption Survey (RECS), still the most current data on this question, asks US households a single-choice question about what kind of thermostat they have: none, manual/non-programmable, programmable, or smart/internet-connected. Those categories don’t overlap – a household picks exactly one.
Broken out that way: 42.6% of US homes have a plain programmable thermostat (the kind with buttons and no app), and only 10.3% have a smart or internet-connected one. That 10.3% is a share of all 123.5 million US homes, it’s a reliable figure statistically, and nothing newer has replaced it – the 2024 version of this survey table isn’t due out until spring 2027. The 40-50% figure everyone quotes is the programmable-thermostat bucket, a different, older, dumber category that gets conflated with “smart” because both involve a screen. A separate Pew survey found 11% of adults report an “AI-featured” thermostat, which lands close to the RECS number but measures a narrower and differently-worded thing – coincidence, not confirmation.
So roughly 1 in 10 US homes has made the jump to a connected thermostat. That’s a smaller market than the ad copy implies, and it means most of your neighbors with a “smart-looking” thermostat are running a programmable unit from 2011.
The device itself doesn’t cost you anything to run
One thing that never factors into the savings math: the thermostat’s own electricity draw. ENERGY STAR’s own certified-thermostat database lists standby power for all 115 currently listed models, ranging 0.02-2.59W with a mean of 0.83W. Run that mean draw nonstop for a year and you get about 7.3 kWh – somewhere around a dollar to a dollar-fifty on your bill, total, for the year. The device is not what you’re paying for and it’s not where any savings or costs come from – it’s a rounding error next to your HVAC system’s real energy use.
Smart lighting tells the same story: independent DOE-cited testing of 31 domestic smart lamps found networking-only standby draw of 0.2-2.4W, averaging 0.4W (CSA Group, citing 2016 DOE test data). Thermostat on the wall or bulb in the socket, the always-on networking chip inside sips power at a level you will never see as a line item. If a smart thermostat is going to save or cost you money, it’s going to do it through how it manages your furnace and AC compressor, not through what it draws itself.
How to tell if one will pay off in your house
Before you spend $150-250 on a thermostat plus install, run this check. It takes ten minutes and it will tell you more than any review will.
Check what your current thermostat is doing right now
If you already have a programmable thermostat, look at whether a schedule is set and being followed, or whether it’s sitting in a permanent hold at one temperature. A well-configured programmable thermostat leaves very little room for a smart one to improve on – this is exactly the profile of the homes that saved nothing in the Florida field study.
Be honest about whether you’ll use the automation
The national data shows two-thirds of people who own a programmable or smart thermostat never turn on the scheduling. If you know you’ll leave it on a single manual setpoint, the smart features can’t save you anything – you’d be paying for a $150-250 remote control.
Look for the specific waste it can fix
Smart thermostats earn their keep on things a human forgets to do: adjusting the temperature before an empty-house workday, backing off overnight, or catching a vacation you didn’t manually account for. If your household already does these things by habit, there’s less left to gain.
Check for a utility rebate before you buy
Many utilities still offer $25-100 rebates for ENERGY STAR-certified smart thermostats, holdovers from programs built around the higher assumed savings numbers. A rebate can cut the payback period substantially even if your real-world savings land at the measured 9-10% range rather than the marketed 20%.
Pick a model, then set the schedule
If the first four checks say yes, go pick a specific model – see our guide to the best smart thermostats for which one to buy – and then spend the ten minutes setting a real schedule instead of leaving it on the default. The device does nothing for you sitting in “hold” mode.
The verdict
Are smart thermostats worth it? For most houses with genuinely inconsistent temperature habits, yes – just budget for measured savings in the 9-10% range on your heating and cooling bill, not the 20% on the box, and expect a real chance of landing near zero if your habits were already decent. For a household that already runs a tight schedule, or that’s going to leave the thing on one setting forever, it’s a $150-250 remote control with a nice app.
The honest pitch is: this is a device that fixes forgetfulness, not a device that fixes physics. If forgetfulness is costing you money right now, it’ll pay for itself. If it isn’t, no amount of machine learning in the thermostat is going to invent savings that weren’t there to begin with.