A smart thermostat only helps if it works with your heating and cooling system. ENERGY STAR's advice starts with compatibility and power, then moves to features.

This guide is based on the public sources listed at the end. We have not tested the products or services mentioned.

This is a short reference page. The full guide is Wi-Fi, Cooling and Smart Home Basics.

Compatibility

  • Most forced-air systems installed after 1975 work.
  • Oil furnaces or boilers may need an adapter.
  • Variable-speed, multi-stage or zoned systems usually need a thermostat built for them, and often a professional.
  • Most smart thermostats do not work with baseboard, biofuel or in-wall heaters. Thick wires for line-voltage control suggest an incompatible system.

Power

Most models draw steady power from a "common wire" (C-wire) at the control board. Without one you may need an adapter or have fewer choices.

ENERGY STAR certified models

These have been tested on field data for savings across climates and must enter a low-power standby when inactive.

Features named

Learning schedules, geofencing (which uses phone location with your permission), vacation mode, automatic updates, temperature or occupancy sensors and voice assistants. ENERGY STAR does not discuss privacy policies, so read the maker's before you buy.

Savings

ENERGY STAR says the average US household spends over $900 a year on heating and cooling and that homes with high bills could save up to about $100 a year. Prices run from about $50 to $300, and many utilities offer rebates. Treat "up to" figures as upper limits.

Installation

You can do it yourself or use an electrician or HVAC professional. As general safety advice, not from the ENERGY STAR page, switch off power at the breaker before touching wires.

Controllers for room AC and mini-splits

Those use a different kind of product. Check the AC maker's compatibility list. See our guide to smart AC controllers.

Last checked: 15 October 2026. Sources: ENERGY STAR, how to choose a smart thermostat.