What Does a Heat Pump Cost to Run Through a Cambridge Winter?

The short version

For a typical three-bedroom Cambridge home that needs about 12,000 kWh of heat a year, a well-designed air source heat pump costs roughly £1,000 a year to run on a standard tariff at October 2026 prices, against about £1,170 for a gas boiler including its standing charge. On a tariff with cheaper off-peak electricity, the heat pump figure drops to around £700.

The rest of this guide explains where those numbers come from and why Cambridge’s climate makes good design especially important.

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Cambridge’s climate and heat pump efficiency

Heat pumps draw heat from outdoor air, and they do it less efficiently as the air gets colder. Cambridge is dry, but its winters are frostier than most of England’s. The Met Office station at NIAB records around 52 air-frost days a year and an average January overnight low just under 2°C. Bristol, by comparison, sees about 33.

What this means in practice:

• A heat pump in Cambridge achieves a slightly lower seasonal efficiency than the same model in a milder western city. We use 3.1 below; a carefully designed system with generous radiators can beat 3.5.
• On frosty mornings the outdoor coil ices and the unit runs short defrost cycles. These use a little energy but are normal.
• The dry air helps. Icing is worst in damp air just above freezing, not in dry cold, and Cambridge’s low humidity in clear frosty spells keeps defrosting less frequent than you might expect.

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A year of running costs, month by month

Heat demand is not spread evenly through the year. Here’s how 12,000 kWh of space heating and hot water might split across the year for a Cambridge semi, with heat pump costs at a seasonal average of 3.1 and 26p per kWh.

Period	Share of annual heat	Heat pump (standard tariff)	Gas boiler (excl. standing charge)
December – February	45%	£460	£480
March – April, November	30%	£300	£320
May – October (mostly hot water)	25%	£250	£265
Year	100%	£1,010	£1,065

Add the gas standing charge of about £108 a year to the gas column if you’d otherwise keep a gas supply only for heating. That brings the gas total to about £1,170.

The table spreads the seasonal average evenly across the year. In reality the heat pump runs a little less efficiently in the coldest weeks, when it costs about the same as gas, and better than average in spring and autumn, which is where most of the saving builds up.

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Tariffs make the biggest difference

Several energy suppliers offer tariffs with cheaper electricity at night or outside the evening peak, aimed at heat pump and electric vehicle owners. A heat pump can pre-heat the house and the hot water cylinder in the cheap hours, then coast through the expensive ones.

If you can average around 18p per kWh across your heating, the Cambridge example above falls from about £1,010 to about £700 a year. That’s a saving of roughly £470 a year against gas.

Tariff names and rates change often, so compare what’s on offer when your heat pump is commissioned rather than relying on a figure in an article.

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Flow temperature: the setting that matters most

The cooler the water going round your radiators, the more efficient the heat pump. A system designed for 45°C might average a SCOP of 3.5 in Cambridge; one running at 55°C might only manage 2.8. For our 12,000 kWh home, that’s the difference between about £900 and £1,130 a year on a standard tariff.

That is why installers size radiators carefully. In Cambridge’s older gault-brick terraces, with their solid walls, upgrading three or four radiators is often what makes a 45–50°C design possible.

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Hard water and hot water costs

Cambridge Water’s supply comes overwhelmingly from the chalk aquifer and runs at around 286–295 mg/l of calcium carbonate — hard to very hard. Scale on a cylinder’s heating coil makes the heat pump work harder to heat your water. A heat pump-rated cylinder with a large coil, plus a scale reducer if your kettle furs up quickly, keeps hot water costs down over the years.

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Landlords and bills-included lets

Much of Cambridge’s housing is let, often with bills included. If you pay the energy bills, a heat pump on an off-peak tariff can cut your costs every month. Give tenants simple guidance: leave the heating at a steady temperature rather than turning it off and on.

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Keep reading

• Payback period — when the savings cover the cost
• Heat pump vs gas boiler over 15 years — the full comparison
• Do heat pumps work in cold weather? — what really happens on a frosty Cambridge morning