Running cost comparisons get argued about because both sides quote true figures from different assumptions. The honest answer is that it depends on three things: the efficiency your system actually achieves, the unit prices you pay for electricity and for your current fuel, and how well the house holds heat.
Here is the way to think it through, using the arithmetic rather than a promise. We install both gas boilers and heat pumps, so we have no reason to talk you into either.
The efficiency comparison in plain numbers
A modern condensing gas boiler running well achieves somewhere near 90 percent efficiency in practice, so a unit of gas buys about 0.9 units of heat. A well designed heat pump achieves a seasonal efficiency of roughly 300 to 400 percent, so a unit of electricity buys three to four units of heat.
The catch is that electricity costs more per unit than gas. Divide your electricity unit price by your heat pump's seasonal efficiency, and divide your gas unit price by 0.9, and compare the two cost per unit of heat figures. That comparison is the whole argument, and you can do it on your own tariff in two minutes.
Where heat pumps win most clearly
- Homes off the gas grid running on oil, LPG or direct electric heating, where the fuel being replaced is expensive.
- Well insulated homes and newer properties where low flow temperatures are easy to achieve.
- Properties with underfloor heating or generously sized radiators.
- Households with solar generation or a favourable time of use electricity tariff.
- Anyone factoring in the Home Energy Scotland Grant and Loan against the installed cost.
Where a boiler may still be the right answer
A poorly insulated solid wall property with small radiators, a tight plant space and mains gas at the door can be an expensive heat pump project and a cheap boiler one. In that situation the sensible sequence is often insulation first, then reconsider. We would rather tell you that at survey than sell you a system that disappoints.
There are also practical cases: a failed boiler in January with no heat in the house is a repair or replacement decision, not a three month design project. Heat pump work is planned work.
Costs that are not fuel
- Annual servicing is needed for both, and both benefit from clean system water and correct inhibitor dosing.
- A heat pump has no gas safety obligation, but it still needs maintenance to hold its efficiency.
- Gas boilers carry warranties up to 12 years on qualifying Vaillant installations through our Advanced Installer status.
- Radiator or cylinder upgrades are a one off capital cost, not a running cost, and belong in the payback sum separately.
Frequently asked questions
- Will a heat pump definitely cut my bills?
- Not automatically. It depends on your tariff, your current fuel and the efficiency the system achieves. Replacing oil, LPG or direct electric heating usually shows the clearest saving. Replacing mains gas is a closer comparison and depends heavily on the design and the house.
- What efficiency should I expect in Scotland?
- A properly designed and commissioned system in a Scottish home should achieve a seasonal figure in the region of three to four units of heat per unit of electricity. Poor design, undersized emitters and high flow temperatures are what pull that figure down.
- Does the grant change the comparison?
- Substantially. The Home Energy Scotland Grant and Loan offers grant funding of up to 7,500 pounds for qualifying households, with an optional interest free loan alongside it, which changes the capital side of the sum rather than the running cost side. We handle the application as part of the job.
- Can I keep my gas boiler as a backup?
- Hybrid arrangements exist and occasionally make sense, but they add complexity and can affect grant eligibility. We will talk it through properly at survey rather than ruling it in or out by default.
Get the comparison run on your own house
Send us your current fuel, roughly what you spend on heating a year, and your postcode, and we will tell you whether a heat pump is worth surveying.