Smart Thermostat Savings Calculator

Defaults last checked: October 29, 2026. Results are estimates.

Smart thermostats save energy in a fairly unglamorous way: they turn the heating or cooling down when nobody needs it, and they make it easy to keep doing that. How much that’s worth depends on what you spend on heating and cooling now and how well you already manage it. This calculator gives you a quick, honest estimate.

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How to use it

  1. Choose your country.
  2. Enter your yearly heating and cooling spend. For the US we start with ENERGY STAR’s figure that heating and cooling cost the average household “more than $900 a year.” For the UK we start with Ofgem’s typical gas use of 9,500 kWh at the current cap rate of 7.97p, which is about £757. That figure includes hot water and cooking, so your heating-only spend will be somewhat lower. Use your own bills if you can.
  3. Check the expected saving. The default is 8%, ENERGY STAR’s average for certified smart thermostats, based on real-world data from installed devices.
  4. Enter the price of the thermostat including installation.

The formula

  • Yearly saving = heating and cooling spend × expected saving %
  • Monthly saving = yearly saving ÷ 12
  • Simple payback = thermostat price ÷ yearly saving

Worked examples

United States. $900 × 8% = $72 a year, or $6 a month. A thermostat costing $200 installed pays back in about 2.8 years. ENERGY STAR notes that savings may be greater depending on climate, comfort preferences, occupancy and your heating and cooling equipment.

United Kingdom. £757 × 8% ≈ £61 a year. Because that spend includes hot water and cooking, the real figure for heating alone will be a little lower.

When the saving is smaller (or bigger)

The 8% average hides a wide range.

  • You already use a schedule. If you already turn the heating down at night and when you’re out, a smart thermostat has less to add.
  • You have a heat pump. Deep set-backs can backfire, because the heat pump works harder to recover, sometimes using backup electric heat. Smaller set-backs and weather compensation usually work better. Our guide to smart thermostats for heat pumps explains which settings help.
  • Your home is often empty. Geofencing and occupancy sensing can save more than average here.
  • Your boiler supports modulation. In the UK, an OpenTherm-compatible thermostat can let a condensing boiler run cooler and more efficiently, which is a separate saving from scheduling.

What the result doesn’t tell you

  • The calculator applies one percentage to your whole spend. In reality, savings on heating and cooling can differ.
  • Some energy companies offer bill credits for letting them adjust your thermostat at peak times. That isn’t included.
  • A thermostat that’s set and forgotten saves more than one that’s constantly overridden.

FAQ

Do smart thermostats really save 8%?

On average, according to ENERGY STAR’s field data for certified models. Some homes save more and some save less, depending on climate, habits and equipment.

Is a smart thermostat worth it with a heat pump?

Often yes, but for a different reason: good control of flow temperature and gentle schedules, not deep set-backs. Check compatibility before buying.

What’s the cheapest way to get most of the saving?

Use the schedule on the thermostat you already have, and lower the set-point by a degree if you’re comfortable. A smart model mainly makes this easier to stick to.

Should I count installation in the price?

Yes. If you need an electrician or a heating engineer, include their fee so the payback is realistic.

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