The Cold Hard Facts About Heat Pumps

What really happens when Britain electrifies heat

Heat pumps are central to Britain’s plan to decarbonise home heating.
They are often sold as cheaper, cleaner and ready to roll out at scale. But the reality on the ground is more complicated.

This report looks past the hype and into the data. Drawing on government-backed trials and a large independent survey of heat pump owners, we’ve examined how heat pumps actually perform in British homes, how much they really cost to run, and where the risks lie.

What we found is clear: heat pumps can cut carbon dramatically, but they are not the national solution to home heating as around 6 million homes will never be suitable for a heat pump.

At a glance

What this report shows

• Heat pumps do work, but not as efficiently as often claimed

• Running costs are currently higher than gas for many households

• Upfront costs remain a major barrier

• Performance depends heavily on property type and system design

• Electrification of heat will fail without energy market reform

Heat pumps can deliver substantial emissions reductions, but they will not reduce household bills unless we break the link between gas and electricity pricing and the wider energy market is reformed.

Why heat pumps matter

Domestic heating accounts for a huge share of UK carbon emissions. Decarbonising heat is unavoidable if Britain is serious about net zero.

The government’s chosen route is electrification, with heat pumps at its core. Schemes like the Boiler Upgrade Scheme are designed to accelerate adoption, replacing gas boilers with air source and ground source heat pumps.

But policy has raced ahead of evidence. Until now, there has been too little focus on real-world performance, real-world costs and real households.

That’s the gap this research set out to fill.

What the data tells us

Real performance, not brochure numbers

Two major UK government-backed studies now give us measured performance data from hundreds of homes.

The headline figure is the Seasonal Performance Factor (SPF), which shows how much heat is delivered for every unit of electricity used.

• Air source heat pumps typically deliver an SPF of around 2.7 to 2.8

• That’s significantly lower than the designed performance figures often quoted

• Performance drops sharply when homes require higher flow temperatures

This matters because efficiency directly affects running costs.

Running costs: the uncomfortable truth

At today’s energy prices, electricity costs almost four times as much as gas per unit.

Even with an SPF close to 3, this means:

• Running an air source heat pump can cost around 24% more than a modern gas boiler

• Ground source heat pumps can perform better, but at much higher upfront cost

In short: cleaner heat does not yet mean cheaper heat. Electrifying heat without fixing electricity pricing risks shifting higher costs onto households rather than delivering savings.

Carbon savings are real, but not the whole story

Heat pumps do deliver substantial emissions reductions:

• Air source heat pumps cut heating emissions by around 70% compared to gas

• Ground source systems deliver even greater savings

But the full carbon picture also includes:

• Embodied carbon in building upgrades

• Grid reinforcement and infrastructure

• The pace of power sector decarbonisation

Heat pumps are capable of cutting carbon significantly, but high upfront costs and higher running costs remain major barriers to adoption.

Homes matter more than technology

Not every home is ready

Heat pumps work best in homes that are:

• Well insulated

• Low heat-loss

• Able to run low-temperature heating systems

The data shows that many homes require upgrades before a heat pump performs well. In fact, around a third of properties assessed for a major government trial were ruled out for technical or economic reasons.

This raises a serious equity issue: without support for home upgrades, heat pumps risk becoming a solution only for the already well-off.

Noise and visual impact

Concerns about noise are often overstated. Most users report no serious issues, and newer models are significantly quieter.

But placement, planning and quality of installation still matter.

The cost barrier

Even with grants, upfront costs remain high:

• An air source heat pump installation typically costs around four times more than replacing a gas boiler

• Ground source systems cost more still

This is the single biggest obstacle to mass adoption. High capital costs combined with higher running costs risk undermining public confidence in the transition to low-carbon heating.

What needs to change

The evidence points to a simple conclusion: heat pumps can work, but the system around them doesn’t.

To make electrified heat succeed at scale, Britain must:

• Rebalance energy prices so electricity reflects its low-carbon advantage

• Fund insulation and heat-loss reduction as standard, not optional extras

• Focus on quality of design and installation, not just headline install numbers

• Be honest about where heat pumps work best and where alternatives may be needed

The bottom line

Heat pumps are not the problem.
The market they operate in is.

Without reform, households face higher bills, higher risks and higher resistance. With the right changes, heat pumps can become what they should be: a part of a fair, low-carbon energy system.

This report cuts through the noise. The facts are cold, but the direction is clear.