Heat Pumps · Glossary
Seasonal Performance Factor (SPF)
The measured (not modelled) seasonal efficiency of a heat pump installation, including ancillary loads like circulation pumps and immersion top-up.
Seasonal Performance Factor (SPF) is the post-installation, real-world cousin of SCOP. SPF includes everything inside the boundary you choose: H4 SPF includes the heat pump, controls, primary circulation pump and any immersion heater top-up for hot water. That makes it the most honest number when comparing real bills.
The Department for Energy Security and Net Zero's Electrification of Heat trial measured median SPF (H4) of 2.80 for ASHPs and 2.86 for GSHPs across the UK. Our installs in Cornwall typically run higher than that median because we design conservatively (low return temperatures, properly sized radiators, weather compensation enabled).
If you want to track SPF on your own system, ask us about adding an MID-class heat meter on the primary flow and a separate kWh meter on the heat pump's power supply. Many MCS installs include this hardware as standard. See our heat pump installation page.