What does COP mean?
Coefficient of performance is useful heating output divided by electrical input for the conditions being assessed. If a system delivers 4 kWh of heat from 1 kWh of electricity, its COP for that measurement is 4. The same device can have a different COP at another outdoor temperature or heating-water temperature.
What does SCOP mean?
Seasonal coefficient of performance combines performance over a defined seasonal test framework. It is generally a more suitable starting point than a single COP for estimating a whole heating season. Check which climate and output-temperature conditions the published figure represents.
What should I enter?
- For an annual estimate, use a seasonal figure that is appropriate for your installation.
- For a particular operating condition, use a relevant COP and treat annual results as a fixed-efficiency scenario.
- If you have measured seasonal data, divide useful heat delivered by electricity consumed over the same period and measurement boundary.
A product’s SCOP is not a guarantee of the efficiency of every installation. Hot-water production, circulation pumps, controls and backup electric heating may be included or excluded depending on the source of the figure. Make the heat-demand and electricity boundaries consistent.
Why not calculate COP from the weather alone?
Outdoor temperature is only one input. Device design, heating-water temperature, part-load behaviour, humidity, defrost and system controls can matter too. This tool therefore asks you for an efficiency value rather than applying a universal temperature penalty.
Try a sensitivity check
For 12,000 kWh of annual useful heat, efficiency 3 needs 4,000 kWh of electricity, efficiency 4 needs 3,000 kWh, and efficiency 5 needs 2,400 kWh. Try a plausible lower and higher figure in the heat pump calculator to see how much your result depends on that assumption.
Background on system performance: Energy Saving Trust. See also our calculation methodology.