Heating Temperature Savings Calculator

Explore how changing an indoor heating temperature affects a simple heat-loss model. Use your own space-heating cost and outdoor-temperature assumption to see the modelled difference.

How to use Heating Temperature Savings Calculator

1. Choose the currency used for results. 2. Enter space-heating usage cost only, excluding hot water and standing charges. Choose comparable indoor and outdoor temperatures for the period you are modelling. 3. Change a value to update the results, or select Calculate. Review the chart and notes with the total. 4. Use Copy results, Share results or Download result graphic to keep the answer. Shared links include your figures. 5. Reset restores the editable example inputs.

Why use this tool?

There is no single bill-saving percentage that applies to every one-degree change in every home. The temperature difference between indoors and outdoors is one reason the effect varies. This calculator lets you explore that relationship transparently. It is useful for a scenario, not a promise of savings. A well-controlled building on a mild day is different from one with changing ventilation, occupancy or heating hours. Treat the result as one simplified view of the heating load, then compare it with actual use when you have measurements.

How the calculation works

The model assumes space-heating cost is proportional to the indoor–outdoor temperature difference. Proposed cost = current space-heating cost × (proposed indoor temperature − outdoor temperature) ÷ (current indoor temperature − outdoor temperature). The difference is a modelled saving or increase. Current indoor temperature must exceed outdoors, and the proposed temperature must not fall below outdoors in this model. Weather, heating hours, boiler efficiency, solar gains, ventilation and occupancy are assumed unchanged. Standing charges and hot water are excluded; the model does not recommend a room temperature.

Example

With £1,000 of annual space-heating usage cost, current indoors at 20°C, proposed indoors at 19°C and an outdoor assumption of 7°C, the model gives £1,000 × 12 ÷ 13 = £923.08. The modelled saving is £76.92 a year. Different outdoor conditions produce a different percentage.

Practical tip

Run a few outdoor-temperature scenarios rather than treating one average as certain. Do not put the whole energy bill into the cost field when only part of it is space heating.