The smart thermostats that actually save money — measured, not marketed

Ecobee's room sensors remain the killer feature: the thermostat targets the average temperature of the rooms you actually occupy, not just the hallway where the unit is mounted. In our 90-day test on a two-story home, this alone made the upstairs bedrooms 2–3°F more comfortable without a runtime penalty.

The Premium tier adds an air-quality sensor and built-in Spotify (you'll never use it). Native Apple Home, Alexa, Google, and SmartThings support means you won't be locked in. For comfort in any home with hot or cold rooms, this is the pick.

The 4th-gen Nest is the first time Google's auto-schedule has felt genuinely smart out of the box. After about a week of leaving it alone, our test unit had inferred wake/sleep/away patterns and reduced HVAC runtime by 12% over the prior month. Matter support arrived in firmware late last year.

Where it still trails Ecobee: room sensors are an additional $99 each, and the app's data export is weaker. If you want set-and-forget more than per-room control, Nest is the better choice.

The T9 is the value pick that doesn't feel like one. Room sensors are around $40 (vs $99 for Nest's), HVAC compatibility is the broadest in the category, and Honeywell's reputation for reliability is well-earned across our long-term install base.

The app is functional rather than beautiful and Apple Home support requires a workaround. If you're on a budget and want sensors, this is the pick.

Most smart thermostats can't drive a mini-split or high-voltage baseboard system; Mysa is purpose-built for both. The line-voltage version handles up to 4,000W of resistive baseboard load, the heat-pump version speaks the right protocols to two-stage and inverter-driven systems, and HomeKit support is native.

Aesthetics are minimalist (no big display) and the app, while clean, lacks the data depth of Ecobee. If you have a heat pump or baseboards, this is one of the few thermostats worth installing at all.