COP and SCOP explained in plain English
What COP and SCOP mean on heat pump quotes, how they affect running costs, and what to ask if the numbers look optimistic.
Plain analogy
A heat pump moves heat rather than burning fuel. COP 3 means about 3 kWh of heat for each 1 kWh of electricity, under the conditions on the label or estimate.
COP vs SCOP
COP is a snapshot (often at a mild outdoor temperature on a data sheet). SCOP blends colder and milder weather across a season. Running-cost lines on quotes usually use SCOP.
Link to your bill
If space heating plus hot water need D kWh of heat per year and SCOP is S:
Electricity for heating ≈ D ÷ S kWh, then multiply by your unit rate.
If the installer uses a cheap tariff or counts solar offset, your real bill can differ. Ask for the figure on your normal tariff.
Flow temperature
Lower flow temps (often with upgraded radiators or underfloor) tend to help SCOP. Pushing 55°C+ through old radiators often pulls SCOP down. The quote should say which emitters are assumed.
If SCOP looks high next to a high flow temp
Ask the installer to explain both numbers together. Assumed SPF/SCOP that looks optimistic for the stated flow temperature is a claim to check, not proof the system will fail.
Common questions
What SCOP is realistic for UK retrofits?
It varies widely. Many retrofits sit roughly in the high 2s to low 3s depending on property and flow temp. Very high figures deserve a clear explanation, not automatic dismissal.
Can I check annual electricity from SCOP?
Roughly yes. Annual heat kWh divided by SCOP gives approximate annual electricity for heating, then add standing charges and auxiliary use.
Related guides
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