What should I replace my old gas boiler with? Leave a comment

With the Prime Minister’s announcement (September 2023) to ditch the date for a ban on the sale of new gas boilers (originally planned for 2035), you may be wondering what to replace your existing boiler with once it needs replacing.  Should you go for a like-for-like replacement or a boiler that is hydrogen-ready?  Or a hybrid system that includes both a gas boiler and a heat pump or go all out and get a heat pump installed to meet all your home’s need for heat?  In this blog, we look at the options and share our thoughts on the options available now for homes on the gas network.

New Gas Boiler

With no date in sight on the sale of new gas boilers and no government plan for the removal of existing gas boilers, there is no legal reason why you shouldn’t opt for a like-for-like replacement of your existing gas boiler.  Chances are that your new boiler will be more energy efficient than your old one (with a difference of 35% in efficiency between the best and the worst boilers) meaning savings in both your fuel bill and carbon emissions.

It is also likely to be the cheapest option both in terms of the installation and running costs (save for a heat pump), while gas remains substantially cheaper than electricity and the one that involves the least amount of hassle.  New gas boilers are easy to find with lots of competition on price.  The technology is well known and there is a nationwide network of installers. With an expected lifetime of 15 years, you won’t need to consider an alternative until the next replacement of your heating system is due.  The downside of this option is that you’re not doing as much to tackle climate change as you could with a heat pump.

For more information on the options when replacing an existing gas boiler and the potential fuel savings read this page on the Energy Saving Trust website.

Hydrogen Boiler

If you’ve been looking to replace your boiler, you may have noticed that many are being marketed as ‘hydrogen blend ready’.  What this means is that the boiler can run on a mixture of natural gas and hydrogen at an 80:20 blend, in anticipation of hydrogen being introduced to the gas grid (not expected to begin until 2028 at the earliest).  The reality is that this is nothing new, with all boilers in the UK being legally required to operate using a hydrogen blend since the mid-1990s.

Indeed, concern about customers being misled by boilers being marketed in this way has now reached the point where the Competition and Markets Authority has launched an investigation into claims being made by boiler manufacturer Worcester Bosch. For more, see this Government’s press release of 17th October 2023.

The UK government has proposed that all new boilers sold from 2026 should be able to switch to run on 100% hydrogen, with pilots due to take place over the next couple of years.  Only once these pilots have been successfully completed, will a decision be made by made by the government whether to switch to 100% hydrogen heating.

Finally, take a moment to consider the hydrogen will come from, the potential cost, and the other sectors within the economy that will be competing for supplies of hydrogen.  Most hydrogen (referred to as grey hydrogen) being made now comes from methane or natural gas, making it no better for the environment than these fossil fuels.  Only hydrogen formed from water through electrolysis with electricity generated from renewable sources – green hydrogen- will have less of an environmental impact than natural gas.

For more on this fascinating topic have a read of this article from Which? and our blog on The Future of Hydrogen Application in the UK.

Hybrid Heat Pump

A hybrid heat pump is a heat pump that is used alongside another heating source, typically a gas or LPG boiler.  It could be installed alongside your existing gas boiler, or installed at the same time as a new one is being installed. So rather than a replacement for your existing boiler, the heat pump is an add-on. To keep capital and running costs down, a hybrid heat pump isn’t usually sized so that it can meet all your needs for heat.

The rationale behind having a hybrid system is that the heat pump can more efficiently provide most of your heating needs than the boiler and when it can’t (like when the weather is very cold) the boiler takes over. 

With sophisticated heating controls, your heat could come from either the heat pump or the gas boiler depending on the fuel cost at the time.  The boiler could also be used to meet your needs for hot water.  Our blog, Can I get my hot water from an air source pump? has more on this topic.

A gas boiler alongside a heat pump might be recommended to you by an installer because your home’s heat demand is very high – perhaps due to its size or because you haven’t been able to insulate it as recommended (remember always to take the fabric first approach- insulate before installing a heating system).  An example of this would be if your house was listed.

Further information on this topic can be found on the Energy Saving Trust website.

Heat pump only

A full replacement of your existing gas heating system for a heat pump (whether ground or air) is a substantial investment.  Plus, you only really want to be installing a heat pump in a property which already has a good level of insulation (although a high-temperature air source heat pump is an option – see our blog on this topic).

Heat pumps run on electricity, rather than gas. The reason that they are better than the environment and your pocket is down to the compressor, which enables the heat pump to produce 2,3 or 4 units of heat for every unit of electricity put in (much better than other sources of electrical heating, like night storage or panel heaters with their 1:1 ratio).

Anyone thinking of having a heat pump installed in their home should look at the government’s Boiler Upgrade Scheme (BUS).  To encourage greater, take up (following disappointing figures from last year) the government recently announced that the amount of the grant will increase on 23rd October 2023 to £7,500 for both air and ground source heat pumps (up from £5,000 and £6,000 respectively).  However, you cannot get a grant for a hybrid system.

Further information on what a heat pump is and how it works can be found in our blog, What an Earth is a heat pump?


If your existing gas boiler needs replacing, you have two main options for replacement: either replace it with a new gas boiler or bite the bullet and go all electric with an air or ground source heat pump.  With a grant of £7,500 now available the cost difference between getting a like-for-like gas boiler replacement and a heat pump has significantly narrowed.

Hydrogen boilers are not yet available, and it will be several years before there is enough hydrogen in the gas being supplied to the UK’s homes for them to be needed.  There is no need to pay a premium for a hydrogen blend-ready boiler as all new boilers should have this feature in any event.

Unless you are living in a particularly large property or one that is hard to heat, there would appear to be little advantage in going for a hybrid system, by the addition of a heat pump to work alongside your existing boiler.  Better to go for a full heat pump system and get the BUS grant to help you meet the cost.

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