Smart Thermostats and Savings: What Studies Show

What independent studies actually found

The clearest evidence comes from a third-party study in Indiana. Researchers placed 300 Nest smart thermostats and 300 standard programmable thermostats in similar homes. All homeowners received proper training first — which removed the usual human-error advantage that smart thermostats have. Even so, Nest users cut heating gas use by 12.5%, versus 5% for programmable thermostat users. Cooling electricity savings were close: 13.9% for Nest versus 13.1% for programmable thermostats. The smart thermostat’s built-in sensors and Wi-Fi let it adjust temperatures on its own, without needing the homeowner to program it correctly.

A separate Nest internal study used real utility data from 735 homes for gas and 624 homes for electricity. It found average gas savings of 10% and cooling savings of 17.5% after one year. Nest is now part of Google. Google has a business reason to show good results, so treat those numbers as a high-end estimate, not a typical outcome.

Why smart thermostats outperform programmable ones

Programmable thermostats sound good in theory but often backfire. A Florida Power & Light study of 400 homes found that the 56% of participants who actually used the programming feature consumed 12% more energy than those who left the thermostat on a fixed hold. The reason: people set overnight temperatures too low by mistake, running the system harder than a simple hold would have.

Smart thermostats sidestep this problem in two main ways. First, they use occupancy sensors — typically passive infrared — to detect when no one is home and pause heating or cooling automatically. Second, learning algorithms build a schedule from your actual behavior rather than requiring you to program one. If your household routine changes, the thermostat adjusts over time. The device does the work that most people never do correctly with a programmable model.

Geofencing adds another layer. The thermostat reads your phone’s GPS location and starts warming or cooling the home before you arrive. ENERGY STAR lists geofencing as a direct way to cut heating and cooling bills. You never return to an uncomfortable house, and the system isn’t running unnecessarily while you’re out.

How much money is actually at stake

ENERGY STAR states that heating and cooling account for almost half of the average American household’s annual energy bill — more than $900 a year. That baseline matters because percentage savings apply to that heating and cooling portion, not your total bill.

Illustrative example (checked arithmetic): If your household spends $900 per year on heating and cooling, a 12% reduction saves $900 × 0.12 = $108 per year; a 17% reduction saves $900 × 0.17 = $153 per year. These numbers are just examples. Your real savings depend on your thermostat habits, home insulation, local climate, and utility rates.

ENERGY STAR certified smart thermostats are also built to work with utility demand-response programs. In these arrangements, your utility briefly adjusts your thermostat during peak grid demand in exchange for bill credits or rebates. To find programs near you, use the ENERGY STAR Rebate Finder at energystar.gov with your ZIP code, or contact your electric or gas utility directly. No specific rebate dollar amounts are confirmed in the evidence reviewed here, so no payback period can be stated with confirmed figures.

What affects whether you actually save

Savings vary widely from home to home. Results differ based on how the thermostat was set before installation. They also depend on how often people are home, the features of the house, and local weather. A household that already kept a tight manual schedule will see smaller gains than one that left the thermostat at one temperature year-round.

Broader home efficiency matters too. Your heating and cooling system’s energy use depends on insulation, duct condition, window quality, and system age. Those are all outside the thermostat’s control. A smart thermostat runs your existing system more efficiently, but it cannot fix heat loss through walls or windows. Pairing a smart thermostat with basic weatherization gives the best combined result. For a related look at how always-on connected devices affect your energy use, see how smart plugs handle standby power.

Check the thermostat maker’s compatibility tool before you buy to make sure your system will work with the model you choose.

Vendor claims versus field results

Ecobee’s internal energy model projected 23% savings on heating and cooling. Nest’s internal model claimed 20%. Both compared against a home kept at one fixed temperature all the time — a best-case baseline, not a typical one.

Real-world studies using actual utility data produce lower numbers: 10–17.5% in Nest’s own field study and 12.5% heating savings in the Indiana third-party study. One review of smart thermostat research found that field studies show savings, but those numbers are lower than what computer models predict. Manufacturer figures are high-end estimates. Treat them as a ceiling, not an expectation.