Insulation payback calculator

Estimate insulation savings from an assessment of how much useful heat the work could save each year. Useful heat means heat delivered to your home. It is different from fuel or electricity bought to produce that heat.

Collect the assessed yearly heat saving, heating performance, tax-inclusive fuel price, installed quote, confirmed non-federal rebate and any extra yearly maintenance. Use the same home, proposed work and operating conditions for all of these figures.

The calculator converts the saved heat into avoided purchased energy. It then estimates the yearly money saved and a simple payback period. It does not work out heat savings from insulation thickness or floor area, and it does not choose the right insulation for your home.

Avoided purchased energy (kWh/year) = assessed annual useful heat saved ÷ heating efficiency fraction or COP. Net annual saving = avoided purchased energy × heating fuel price per kWh − extra annual maintenance. Simple payback (years) = (installed price − confirmed rebate) ÷ positive annual net saving.

COP (coefficient of performance) is useful heat delivered divided by electricity input. SCOP is this ratio over a season. A ratio of 4 means 4 kWh of heat per 1 kWh of electricity; use the ratio itself, without a percent conversion.

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.

Read the avoided energy and net yearly saving before relying on payback. Payback divides the net installed cost by a positive yearly saving. A zero or negative saving cannot repay that cost in a finite time.

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 heat saved is supplied by your assessment; the calculator does not infer it from floor area or insulation thickness. Enter 0.90 for 90% efficiency, or seasonal COP for a heat pump.

No federal 25C credit is included for 2026 projects. Confirm any other rebate separately.

The estimate holds prices, heat savings and maintenance constant. Simple payback excludes finance, replacement, wear and future price changes. It does not predict an individual future bill. A result can change greatly if the assessed heat saving or fuel price changes.

Keep the rebate separate from the quote unless it is already taken off. Enter zero for a personal cost or rebate that does not apply. The example shows arithmetic, not a typical saving for a home.

This US estimate uses dollars and the fuel price per kWh requested by the form. Use your own tax-inclusive price for the heating fuel being saved. If your supplier bills another unit, convert that price before entering it.

A general electricity average is not your heating tariff. No federal credit is automatically deducted. Use only a confirmed non-federal rebate in the rebate field, and check the linked official sources before making a purchase.

Ask a qualified building or energy professional to assess heat savings and suitable insulation before buying. They should review the proposed work and the home rather than treating an example as a survey.

Take the heat-saving assessment, heating-system details and written quote. Ask them to check the heating performance used and identify costs outside the estimate. Confirm any rebate with its provider. The calculator does not approve building work or decide eligibility.