The short answer

Savings come from setback, not from the device. Estimate what a lower setpoint for the hours you are away would save on your actual heating bill, then compare with the thermostat's price plus any installation. Manufacturer headline percentages are averages across households unlike yours.

When it can pay back

  • You have a conventional forced-air furnace or heat pump with a low-voltage thermostat, and nobody has been setting it back.
  • The house is empty on a regular pattern that a schedule or occupancy sensing can follow.
  • Your heating fuel is expensive per unit of heat, so each degree-hour of setback is worth more.
  • Your utility runs a rebate or demand-response programme that lowers the purchase price. Check the utility's current terms; eligibility is not assumed here.

When it cannot

  • Electric baseboards: these are line-voltage circuits and need a line-voltage thermostat per heater, a different product category, often with an electrician. A low-voltage smart thermostat does not fit.
  • Heat pumps in cold climates: a deep setback can trigger expensive auxiliary heat on recovery; the thermostat must be configured for the system, and gains are smaller than for a furnace.
  • You already set back manually, or someone is home all day: the device automates what you are doing already.
  • The wiring lacks a common (C) wire and the manufacturer's compatibility check says an adapter or new wire is required; that adds cost and may need a technician.

Checks before buying

  1. Photograph your current thermostat's wiring and run the manufacturer's official compatibility checker for the exact model you are considering. Do not rely on a generic tutorial.
  2. Work out the saving yourself: how many hours a week can the setpoint drop, by how many degrees, on what fuel? Put the heating-fuel share of your bill from the diagnostic against that, not against the whole bill.
  3. Add installation cost if you will not do it yourself, and divide the total by the annual saving for a payback in years. Zero or negative saving means no payback under those inputs.
Why there is no product recommendation here

This site names a product only after matching the exact model to its manual and a verified US listing, and a thermostat also has to match your system's wiring. That work has not been done for any thermostat, so this page explains the decision without recommending a device. Space heaters have their own arithmetic on the heater page, and the calculator covers any plug-in load.

Sources and evidence

What we are relying on

Energy cost for a steady load = watts ÷ 1,000 × hours per day × days × your rate in dollars per kWh.
Arithmetic method, not a measurement. Appliances that cycle on and off need measured kWh or actual runtime, not nameplate watts × 24 hours.

What this page does not establish

  • No thermostat model, savings percentage or rebate is cited; those need current manufacturer compatibility tools and utility programme terms at the time of purchase.
  • The setback method is a way to estimate; actual savings depend on the building, weather and behaviour.

Sources

  1. Estimating appliance and home electronic energy use, Virginia Cooperative Extension. Calculation method; read 2026-09-07.

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