Heat Pump COP & Running Cost Calculator

Replacing a 30-year-old gas boiler with a commercial heat pump used to be an ESG line item. With Climate Change Levy on gas falling, electricity carbon factors declining, and the gap between unit prices narrowing in the right tariff structures, it is increasingly a finance question. A 100 kW heat pump running at a seasonal COP of 3.2 delivers heat at roughly a third of the electricity input, and whether that beats gas on running cost depends on the spread between p/kWh gas and p/kWh power on the actual contracts the site is on.

The number that matters is annual £, not COP in isolation. A school with a 350,000 kWh gas demand pays roughly £21,000 at 6 p/kWh. The equivalent heat pump load at COP 3 needs around 117,000 kWh of power. At 25 p/kWh that is £29,250, at 18 p/kWh it is £21,060, and at 14 p/kWh it is £16,380. The contract terms, the time-of-use shape, and any onsite PV change the answer materially. Plus there is the Boiler Upgrade Scheme grant and the carbon reporting angle for SECR-listed organisations.

Purely Energy advises clients planning electrification on the contract design that makes the engineering case stand up. That includes time-of-use tariff selection for heat pump duty cycles, half-hourly metering on the new circuit, capacity headroom on the existing MIC, and how non-commodity charges land on a load that now runs all winter rather than just the gas meter ticking over. The kit is only one part of the answer. Multi-site operators in particular need a portfolio view, because the COP that works at the Midlands site will look different at the Glasgow site once the heating degree-day profile is added in, and the right tariff for one will be wrong for the other.