Heat Pump or New Gas Boiler? An Honest Comparison

Almost nobody chooses a heating system in the abstract. The decision arrives when a boiler is fifteen years old, the engineer has mentioned the word “uneconomical”, and there is a choice to make before winter: swap like for like, or change the way the house is heated altogether.

Both are reasonable answers. Which one is right depends on your house, your radiators and how long you expect to be living there, rather than on anything either industry says about the other.

What the two actually cost to buy

A new gas boiler fitted into existing pipework is the cheaper installation by some distance. The appliance is small, the work is usually a day, and nothing else in the house needs to change.

An air source heat pump is a bigger job and a bigger bill, but the Boiler Upgrade Scheme closes most of the gap. The grant is £7,500, rising to £9,000 for homes heated by oil or LPG, and the installer claims it so it comes off the price you are quoted rather than arriving later as a rebate. After the grant, heat pumps start from around £3,000. Installs take two to three days.

So the upfront comparison is not heat pump against boiler at full price. It is a boiler swap against a grant-assisted heat pump, and once you look at it that way the numbers are closer than most people expect.

What they cost to run

This is where the detail matters, because the answer is genuinely “it depends on how well the system is set up”.

A modern gas boiler turns roughly 90% of the gas it burns into useful heat. Under the current price cap, gas sits close to 8p per kWh, which puts a unit of heat at a little under 9p. A heat pump runs at a SCOP of 2.5 to 4, meaning it produces that many units of heat per unit of electricity. On grid electricity at around 24p per kWh, a SCOP of 3 gives you heat at 8p and a SCOP of 2.5 gives you nearly 10p.

In other words, a well designed heat pump on a standard tariff lands around gas parity, and a poorly commissioned one running hot comes out worse. The systems that clearly beat gas are the ones on a heat pump electricity tariff, or with solar panels covering a share of the daytime demand, or both. A heat pump is not automatically cheaper to run. It is cheaper to run when the design, the tariff and the controls are all pointing the same way, which is why the survey matters more than the brand.

Off the gas grid, the comparison is not close at all, and the enhanced £9,000 grant reflects that.

What changes in the house

A boiler swap changes nothing you can see. A heat pump might.

Heat pumps work at lower flow temperatures, so some radiators need upsizing to give out the same heat, usually a handful rather than all of them. You need an outdoor unit with clear airflow, and a hot water cylinder if you are coming from a combi. None of that is difficult, but it is space and disruption that a boiler replacement does not involve, and it should be set out plainly in a quote rather than discovered on the day.

When a new boiler is the better call

If you are selling within a couple of years, if the only sensible spot for an outdoor unit is awkward, or if the heat loss survey says your house needs flow temperatures a heat pump will struggle to hold comfortably, a new boiler is the honest recommendation. A heat pump fitted into a house that is not ready for it produces cold rooms and high bills, and nobody wins from that.

If your boiler still has a few years in it, that is also useful information. It buys you time to insulate, to think about solar, and to make the change on your own schedule rather than in an emergency in January.

The practical next step

The thing that settles it is a proper heat loss calculation for your house, radiator by radiator, alongside a straight comparison of both options with real numbers against them. We use subcontractors for parts of some installs, as is standard in this industry, and the design, specification and handover remain ours to manage and answer for.

If you would like both options costed honestly, including the case for sticking with gas for now, our survey is free and carries no obligation.