Smart thermostat savings calculator

Estimate thermostat savings from a lower and higher assessed reduction in yearly heating energy. Start with purchased energy used for heating before the thermostat change. Keep cooking, hot water and other household uses out of that baseline.

Collect the baseline energy, an assessed savings range for your home, the heating fuel price and the full installed thermostat quote. The tool does not turn setback hours into an assumed saving. Different homes and controls can produce different results.

Use the same year and heating system for both scenarios. The two percentages describe your assumptions, not a guaranteed range. Personal amounts start empty. Enter zero explicitly where a price or saving does not apply.

Saved purchased energy = baseline heating energy × entered annual reduction. Saving = saved energy × heating fuel price. Payback bounds = installed price ÷ positive annual saving.

Use a percentage as a fraction once: for example, 50% means 50 ÷ 100 = 0.5. Use 0.5 in the energy formula; do not divide it by 100 again.

Energy prices are entered in pence or cents per kWh unless the field names another unit. Divide by 100 to obtain pounds or dollars. Fixed supply charges are excluded unless explicitly entered. Use tax-inclusive bill prices for personal scenarios.

The higher assessed reduction saves more energy at the same fuel price. A larger saving gives a shorter simple payback. Read the remaining heating cost alongside the saving to see how much of the baseline is still being purchased.

Check the order of the reduction inputs: the lower estimate should be no greater than the higher estimate. Use the percentage saved, not the percentage of heating left. If an assessment describes remaining energy instead, ask for the matching reduction before entering it. Keep both values on the same yearly baseline so the range compares like with like.

These illustrative inputs are separate from your saved answers. Prices, use and performance are held constant for this worked scenario; they are not personal defaults.

The reduction range is an explicit assumption. Setback hours alone do not determine annual savings and no guaranteed default percentage is supplied.

Use heating-only purchased energy from comparable conditions, not whole-home energy including cooking or hot water.

Annual scenarios hold prices and usage constant. Simple payback excludes financing, replacement, degradation and future price changes. There is no finite payback when the annual saving is zero or negative.

A whole-home bill may not identify heating separately. Ask for a suitable split rather than treating every kWh as heating. Keep a note of whether the baseline and reduction are measured or assessed.

The result does not confirm thermostat compatibility, comfort or a safe temperature schedule. Weather, occupancy and existing controls can change actual savings. Invalid edits keep the last valid calculation visible with a warning.

Use the Canadian or UK version that matches your bill, with cents or pence per kWh as labelled. Enter your tax-inclusive heating fuel price. If the fuel is billed in another unit, convert it to kWh before entering it.

This tool uses the heating price you supply. It does not fetch a live tariff, add a rebate or remove fixed supply charges. Source dates describe the supporting method, not verified facts about your home. Check the bill period and quote before relying on payback.

Ask a qualified heating installer to confirm that the thermostat suits the heating system and to assess a realistic yearly reduction. Bring the heating records, proposed control changes and installed quote.

Ask them to explain the assumptions behind the lower and higher estimates. Confirm any work needed beyond the thermostat itself. The calculator does not approve wiring, equipment changes or a temperature schedule; follow the maker instructions and appropriate local requirements.