The Two Numbers That Decide Your Bill
Heat pump running cost comes down to two things: your SCOP (how efficiently the pump turns electricity into heat) and your electricity tariff (what you pay per kWh). Everything else is detail.
A well-designed system running at a SCOP of 3.5 on a smart heat-pump tariff is a completely different proposition to a poorly designed one at SCOP 2.8 on a standard variable tariff — the annual cost can differ by more than half for the same home.
For every 1 kWh of electricity it draws, a well-designed heat pump delivers about 3.5–4 kWh of heat — the rest is free warmth pulled from the outside air.
Worked Example: 12,000 kWh Home
For a typical three-bed semi needing about 12,000 kWh of heat a year:
- Gas boiler (90%): ~£780–£900/yr
- Heat pump, standard tariff, SCOP 3.0: ~£960–£1,100/yr
- Heat pump on Cosy Octopus (blended ~17p/kWh): ~£640/yr
- Highly efficient setup + smart scheduling (SCOP 3.5+): as low as ~£350–£460/yr
On a standard tariff the heat pump is roughly level with gas. On a dedicated heat-pump tariff it wins clearly. This is why we always talk tariffs at the survey, not just kit.
How Smart Heat-Pump Tariffs Work
Tariffs like Cosy Octopus use a triple-dip structure — three cheap off-peak windows a day (typically 04:00–07:00, 13:00–16:00 and 22:00–00:00) at around half the standard rate, and a pricier peak window (16:00–19:00).
The strategy is simple: heat the home and the hot water cylinder during the cheap windows, nudging target temperatures 1–2°C higher to “store” heat in the fabric and cylinder, then coast through the expensive peak. A SMETS2 smart meter and a heat pump you can schedule make this automatic. To access these tariffs you need to be on the relevant supplier with an eligible heat pump and smart meter.
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Add Solar and the Numbers Improve Again
Pair a heat pump with solar panels and much of your daytime electricity becomes free, which is especially useful for the 13:00–16:00 heating window and for hot water. Add a battery and you can store cheap off-peak or surplus solar energy to use during the expensive peak.
Solar plus a heat pump plus a smart tariff is the lowest-running-cost combination available to a UK home in 2026 — and it is exactly the kind of whole-system design we specialise in.
What Pushes Costs Up (and How We Prevent It)
Running costs balloon when flow temperatures are too high, radiators are undersized, the system short-cycles, or weather compensation is not set. Every one of these is a design or commissioning failure, not a fault of the technology.
We carry out room-by-room heat loss calculations, design for the lowest practical flow temperature, size emitters and the cylinder correctly, and commission the system properly with weather compensation dialled in. That is what keeps your SCOP high and your bills low year after year.
Frequently asked questions
For a typical 12,000 kWh home, expect roughly £960–£1,100 on a standard tariff, around £640 on a smart heat-pump tariff, and as low as £350–£460 for a highly efficient system with smart scheduling. Your insulation, SCOP and tariff drive the figure.
For most heat pump homes, yes — the cheap off-peak windows blend your electricity rate down to around 17p/kWh, which typically makes the heat pump cheaper to run than a gas boiler. You need to be an eligible customer with a compatible smart meter and a schedulable heat pump.
Significantly. Solar provides free daytime electricity for heating and hot water, and a battery lets you store cheap or surplus energy for the expensive evening peak. Solar plus heat pump plus a smart tariff is the lowest-cost combination for a UK home.
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