Running-cost calculator
What does it cost to hold a room at 20°C?
Set the room, the weather and your electricity price to see an indicative hourly, daily and monthly cost for heating or cooling, and how that changes across the year.
Tell us about the room
Every field affects the estimate. Change anything and the numbers update instantly.
Fetching the current outside temperature…
- Estimated load
- 0.98 kW
- Electrical input
- 0.23 kW
- Assumed EER
- 4.20
- Indicative capacity class
- 2.0 kW
These figures are an indicative estimate for guidance only. They are not a quotation, a heat-loss calculation or a system design. Real running costs depend on your building, your habits, your equipment and your electricity tariff. James confirms sizing and expected performance at survey.
Cost across the year
How the estimated hourly cost changes as the outside temperature changes, with your settings held constant.
- Heating
- Cooling
- Selected temperature
View the chart data as a table
| Outside temperature | Mode | Cost per hour |
|---|---|---|
| -5°C | Heating | £0.14 |
| 0°C | Heating | £0.09 |
| 5°C | Heating | £0.06 |
| 10°C | Heating | £0.03 |
| 15°C | Heating | £0.01 |
| 20°C | Cooling | £0.06 |
| 25°C | Cooling | £0.09 |
| 30°C | Cooling | £0.13 |
| 35°C | Cooling | £0.18 |
How it works
The assumptions behind the numbers
The calculator estimates the heating or cooling load for your room, divides it by the expected efficiency of a modern air-to-air heat pump at that outside temperature, and multiplies the resulting electrical input by your electricity price.
- Load. Floor area, ceiling height, insulation standard, glazing and sun exposure set the fabric load. Occupants, equipment and room use add internal gains, which matter most when cooling.
- Efficiency. Heating uses a COP that falls as the weather gets colder; cooling uses an EER that falls as the weather gets hotter. Both are interpolated between typical published points.
- Cost. Electrical input in kW multiplied by your price per kWh gives the hourly cost. Daily and 30-day figures come from the hours per day you enter.
- Capacity class. The suggested class is the smallest common unit size that covers the estimated load. Above about 10 kW you are usually looking at more than one system.
This is an estimate, not a quotation. It is not a heat-loss calculation or a system design, and it cannot see your building. For a real figure, book a survey.
Questions
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