Home Energy Audit Savings Calculator

Work out home energy audit savings instantly with clear inputs, formula shown and shareable results.

About Home Energy Audit Savings Calculator

Energy saving measures multiply rather than add: 18% from insulation and 6% from draught proofing give 22.9% combined, not 24%, because the second measure works on the already reduced consumption. Payback is measure cost divided by that annual saving.

Formula

Combined saving

combined = 1 - (1 - s1)(1 - s2); payback = cost / annual saving

Worked example

With the default values below, Home Energy Audit Savings Calculator returns Annual saving of $481.32. Change any input above and every figure here is recalculated in your browser.

Inputs used

Annual energy bill: 2,100
Saving from insulation: 18 %
Saving from draught proofing: 6 %
Cost of measures: 2,800

Results

Annual saving: $481.32
Payback period: 5.82 years
Ten-year net saving: $2,013.20
Combined saving: 22.92% %

Step by step

1Values used
2Combined saving
3Annual saving= 481.32
4Payback period= 5.82 years
5Ten-year net saving= 2,013.20
6Combined saving= 22.92 %

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation or tax into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why do savings not simply add?

Each measure reduces the same heat loss, so the second one has less to work with. This applies to every combination of efficiency measures.

Which measure pays back fastest?

Draught proofing and loft insulation, often within two to three years. Solid wall insulation and glazing take a decade or more.