How Much Does It Really Cost to Run A Heat Pump in Winter?

You've probably heard that heat pumps are cheap to run until it gets cold, and then the bills spike.

It's one of the most common worries we hear, and it's half right.

A heat pump does work harder in January than it does in October. But whether that costs you more than gas has very little to do with the weather.

It comes down to how well the system is designed for your home.

And when the design is wrong, a heat pump really can cost more than gas.

Three Numbers Decide Your Winter Bill

Every heat pump running cost comes down to three things: how much heat your home needs, how efficiently the heat pump makes it, and what you pay for electricity.

The sum is simple. Divide your heat demand by the heat pump's efficiency, then multiply by your electricity price.

Heat demand is set by your home. A draughty Victorian terrace needs far more heat than a well-insulated 1990s semi, and every home needs more in January than in October.

Efficiency is measured as the coefficient of performance, or COP. A COP of 3 means you get 3 kWh of heat for every 1 kWh of electricity you buy.

Over a full year, this is called the seasonal COP, or SCOP.

Electricity price is the one you hear about most. From 1 October to 31 December 2026, the Ofgem price cap sets electricity at 26.32p per kWh and gas at 7.97p per kWh, as averages for direct debit customers.

That gap looks huge. Electricity costs more than three times as much as gas per unit.

But a gas boiler turns roughly 85% of its fuel into heat, so each useful kWh of heat from gas costs around 9.4p.

A heat pump at COP 3 makes the same kWh of heat for about 8.8p. At COP 3.5, it's about 7.5p.

At COP 2.5, it's around 10.5p, and that's more than gas.

That's the honest headline. A heat pump needs to average a COP of about 2.8 or better just to match a gas boiler on a standard tariff.

Get the efficiency right and it costs less to run. Get it wrong and it costs more.

The good news is that efficiency is something a good installer controls.

A heat pump beats gas once it averages a COP of about 2.8.

Cost of 1kWh of heat in pence. Break-even COP 2.8 at the Oct to Dec 2026 price cap

What a January really costs: a worked example

Let's put real numbers on it.

Take a typical three-bedroom semi that needs around 12,000 kWh of heat a year for heating and hot water. January is the hungriest month, and a home like this uses roughly 2,000 kWh of heat in it.

We've used today's price cap rates and kept the efficiency figures realistic for the coldest month, when every heat pump runs a little below its yearly average.

Heating system	January efficiency	Energy bought	Estimated January cost
Well-designed heat pump	COP 3.0	667 kWh electricity	£176
Gas boiler	85%	2,353 kWh gas	£188
Poorly designed heat pump	COP 2.4	833 kWh electricity	£219

Estimated, based on current energy prices (Ofgem price cap, 1 October to 31 December 2026). Excludes standing charges. Actual costs vary with your home, usage and tariff.

The well-designed heat pump beats gas, even in the coldest month of the year.

The poorly designed one costs about £43 more than the well-designed system in a single month.

Same weather. Same house. Same electricity price. The only difference is the design.

There's one more saving the table doesn't show. If you switch to a heat pump and remove your gas supply altogether, you stop paying the gas standing charge, which is currently 29.68p a day, or around £108 a year.

Is COP 3.0 in January realistic? Real-world data says yes. The government-funded Electrification of Heat trial monitored 742 heat pumps across a broad range of UK homes. Air source heat pumps averaged a median efficiency of 2.80 across the year, and still managed 2.44 on days as cold as -6°C.

Those figures include every installation in the trial, good and average. A system designed carefully around your home should do better.

Why some heat pumps cost more in winter than others

If design is the difference, what does good design actually mean?

It starts with flow temperature. That's how hot the water is when it leaves the heat pump and travels to your radiators or underfloor heating.

The lower the flow temperature, the more efficient the heat pump. A system running at 35°C to 45°C performs far better than one pushed to 55°C or more. And you can only run at low temperatures if your home can release that heat into the rooms.

That's why emitters matter. Underfloor heating is ideal because it covers a large area and works well at low temperatures. Radiators work too, but some rooms may need larger ones.

Next comes sizing. A proper room-by-room heat loss survey tells your installer exactly how much heat each room needs on the coldest day.

Undersize the heat pump and it struggles in a cold snap. Oversize it and it switches on and off constantly, which wastes energy and wears out the compressor.

Then there are the controls. A well-set-up heat pump uses weather compensation, which gently adjusts the flow temperature to match the weather outside.

It runs low and steady, rather than blasting heat in short bursts the way a boiler does. That can feel strange at first, but it's how a heat pump does its best work.

Hot water plays a part too. Heating a cylinder needs higher temperatures, so efficiency drops while it's running. Timing it well and sizing the cylinder correctly both help.

Finally, there's commissioning. A heat pump installed with factory settings rarely performs at its best. It needs setting up for your home, your emitters and how you live.

None of this is visible on the day of installation. All of it shows up on your January bill.

How to bring your winter running costs down

Once the system is designed well, the next biggest lever is the price you pay for electricity.

Our worked example uses the standard price cap rate. Most heat pump owners can do better than that.

Several suppliers now offer heat pump or time-of-use tariffs, with cheaper electricity at set times of day. Running your heat pump harder during those windows, and topping up your hot water cylinder while rates are low, lowers the average price of every kWh you use.

A home battery takes this further. It charges overnight at the cheapest rate and powers your heat pump through the expensive evening peak.

In winter, this is where a battery really earns its place. Your solar panels generate less in the darker months, but your battery keeps working every single night.

Solar still plays its part. On bright winter days, panels feed the heat pump directly, and from spring to autumn they cover most of your hot water.

That's the logic behind designing heating, solar and storage as one system rather than three separate purchases. Each part makes the others more valuable.

Insulation is the other quiet winner. Every kWh of heat your home doesn't lose is a kWh you never pay for. Even simple steps like loft insulation and draught-proofing reduce what your heat pump has to deliver on the coldest days.

The bottom line

So, how much does it really cost to run a heat pump in winter?

For a typical three-bedroom home, a well-designed system costs around £175 in January at today's standard prices. That's less than the same heat from gas, before you add a cheaper tariff, a battery or solar.

A poorly designed system in the same home can cost more than gas.

The heat pump isn't the variable. The design is.

At Green Flare, we've been designing and installing heat pumps across Bristol and the South West since 2009. Every system starts with a room-by-room heat loss survey, and we size, set up and commission it around your home, not a rule of thumb.

We're MCS and RECC accredited, and we've partnered with Stiebel Eltron for more than 15 years.

If you'd like to know what a heat pump would cost to run in your home, talk to us. We'll give you real numbers, not a sales pitch.