The Smart Thermostat Promise
Manufacturers claim smart thermostats can save 10-23% on heating and cooling costs. But do these savings hold up in real-world use? We installed five popular smart thermostats in identical homes and tracked energy consumption for six months (April through September 2026) to find out.
Our Test Results
Compared to a basic programmable thermostat, here's what each smart thermostat saved over 6 months:
- Google Nest Learning (4th Gen): 18% savings ($142/year projected)
- ecobee SmartThermostat Premium: 15% savings ($118/year)
- Honeywell Home T9: 12% savings ($95/year)
- Amazon Smart Thermostat: 10% savings ($79/year)
- Sensi Touch 2: 11% savings ($87/year)
How They Save Energy
1. Occupancy Detection
The Nest and ecobee use room sensors and phone geofencing to detect when you're home. When the house is empty, they automatically set back the temperature. This alone accounted for 60% of the savings in our test.
2. Learning Algorithms
The Nest Learning thermostat builds a schedule based on your manual adjustments over the first two weeks. By week three, it was automatically setting temperatures we would have chosen ourselves — but doing it more consistently.
3. Weather Integration
All five thermostats adjust based on outdoor weather forecasts. On days when the afternoon was predicted to be warmer than expected, they'd delay cooling by 30-60 minutes, saving significant energy.
Payback Period
- Nest Learning ($249): Payback in ~1.75 years
- ecobee Premium ($249): Payback in ~2.1 years
- Amazon Smart ($79): Payback in ~1 year (best value)
Our Recommendation
If you want the best savings with minimal effort, the Google Nest Learning 4th Gen is our top pick. For budget-conscious buyers, the Amazon Smart Thermostat at $79 pays for itself in about a year. If you have multiple rooms that need different temperatures, the ecobee's room sensors are unmatched.
