Every smart thermostat box promises 10–23% energy savings. As a contractor, we install dozens of these every month. We pulled energy data from 50 customer installs over the past two years to see what actually happens. The answer: it depends — but mostly yes, with caveats.
The Tested Models
We focused on the four most common units we install in Colorado:
- Google Nest 3rd/4th gen
- Ecobee SmartThermostat with Voice Control
- Honeywell T9 with sensors
- Sensi Touch
The Real-World Results
Average annual heating and cooling savings vs. the previous non-programmable thermostat:
- Homes with consistent occupancy patterns (work 9–5, weekends home): 14–18% savings
- Work-from-home households: 4–7% savings (less to optimize against)
- Homes with multiple zones and proper sensor placement: up to 22% savings
- Homes with poor envelope (drafts, leaks, old windows): 6–9% — the system still has to work hard regardless of when
Why Smart Thermostats Save Money
- Setbacks during away/sleep periods — every 1°F of setback for 8+ hours saves about 1% on the bill. A 6°F night setback alone saves 6%.
- Geofencing — phone-based location detection automatically eases temperatures when everyone leaves.
- Adaptive learning — Nest in particular adjusts based on recovery time, avoiding overshoots.
- Zoning with remote sensors — Ecobee and T9 prioritize occupied rooms, instead of heating/cooling based on a hallway sensor.
Where People Lose the Savings
- Disabling auto-schedules because they “feel cold” — undoing the entire savings
- Setting the same temperature 24/7 — defeating the purpose
- Mounting the thermostat on an exterior wall or near a vent — bad readings, system runs incorrectly
- Skipping firmware updates for years — thermostats genuinely improve over time
Compatibility Warnings
Older two-stage furnaces and dual-fuel heat pump systems need a thermostat that supports them. Nest 3rd gen has reduced support for two-stage equipment after a 2024 firmware update — we now recommend Ecobee or Honeywell T9 for those setups.
Required: A C-wire
All smart thermostats need constant power, supplied by a C-wire (common). Many older Colorado homes don’t have one. We can usually add one during install at a small additional cost, or use a power extender kit.
Xcel Energy Rebates
Xcel offers instant rebates on qualifying smart thermostats and additional incentives for enrolling in their AC Rewards or Saver’s Switch programs. Stack these and the unit pays back in the first year for most households.
Bottom Line
For most Colorado homes, a properly installed smart thermostat saves a meaningful amount each year and typically pays back the unit within 12–18 months. Skip the high-end voice-control versions if you don’t need them — the basic models capture most of the savings.