Heat pump brochures are full of numbers: COP, SCOP, SPF, and ErP ratings. They all describe efficiency, but they measure it in different ways, and knowing the difference helps you judge whether a quote stacks up. Here is how we explain it to homeowners across South East London.
What COP Tells You
COP (Coefficient of Performance) is the ratio of heat produced to electricity used at one specific set of test conditions. A COP of 4 means the unit delivers four units of heat for every unit of electricity it draws.
Why SCOP Is More Useful
SCOP (Seasonal Coefficient of Performance) averages efficiency across a full heating season rather than one test point, accounting for milder autumn days and colder winter mornings to reflect real behaviour over time.
The AirToHeat Standard:
- Grant Aerona and Vaillant AroTHERM Plus ranges are A+++ ERP rated at a 35°C flow temperature.
- We design our systems to target a 400% SCOP (though this remains a standardised laboratory figure).
Where SPF Comes In
SPF (Seasonal Performance Factor) is the metric that actually shows up on your energy bill. Measured in your home over a real season, it accounts for total system power draw: the heat pump, circulation pumps, controls, and hot water immersion backups.
Note: SPF is usually lower than datasheet SCOP because houses aren’t test chambers. A well-designed system keeps this gap minimal.
What Moves the Number in Your Home?
- Flow Temperature: Running radiators at 45°C instead of 55°C makes a massive, measurable difference.
- Emitter Sizing & Insulation: Correctly sized radiators/underfloor heating and proper insulation matter just as much as the unit itself.
- Hot Water & Controls: Demand settings and smart control configurations play a vital role.
Compare Like for Like
When reviewing quotes, check that every COP or SCOP figure comes bundled with its flow temperature, and ask what flow temperature the system has been designed around. That is the honest basis for comparison.
Want us to walk through the figures on your quote?
