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Replacing a coal fired back boiler heating system

Air Source Heat Pumps (ASHPs)

Last Post by Judith 35 minutes ago

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Phleach

(@phleach)

New Member Member

Joined: 2 hours ago

Posts: 2

Topic starter 28/05/2026 8:28 pm [#3027]

Hello all,

I have recently purchased a very run down little bungalow and am in the process of renovating, I will be also be adding an extension on the rear. There is no gas feed to the property and the current heating system is a coal fired back boiler. I was hoping to take advantage of the £7500 grant scheme to replace with an air source heat pump (was thinking underfloor heating in the extension I will build and upgrade of the radiators in the existing property. However upon further investigation it appears a coal fired back boiler replacement is not covered by the grant scheme as only fossil fuels! I am confused as isn't coal/anthracite a fossil fuel?!

Is anybody able to confirm if I am correct and would not be able to get the grant please?

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Coal fired back boiler

Mars

(@editor)

Illustrious Member Admin

Joined: 5 years ago

Posts: 4659

28/05/2026 8:56 pm

Welcome to the forum @phleach. Great question... and I'll be honest, it made me go and look this up properly because I had no clue.

You are right that coal is a fossil fuel... and I think you are wrong that you're excluded. Good news!

It would appear that the the Ofgem Property Owner Guidance is unambiguous on this. For heat pumps, fossil fuel heating systems eligible under the BUS include but are not limited to those fuelled by gas, oil, LPG and coal. Coal back boilers are explicitly listed. Whoever told you otherwise was misinformed. You can verify this directly in the Ofgem guidance document here.

And the official Ofgem application voucher form itself lists coal as one of the fuel types being replaced. Link here.

The GOV.UK eligibility checker is also worth bookmarking too.

So your plan (ASHP with UFH in the new extension and upgraded radiators in the existing bungalow) is viable, grant-eligible and actually a near-ideal setup for a heat pump. You're designing part of the system from scratch, which means you can get the UFH right from the outset and the opportunity to properly size the radiators in the existing part of the building to run at low flow temperatures is exactly what makes a heat pump perform well long-term.

Before anyone sizes anything, make sure a proper room-by-room heat loss calculation is done... as you probably know, it's the foundation of everything else. The community here can help with that conversation when you're ready.

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Phleach

(@phleach)

New Member Member

Joined: 2 hours ago

Posts: 2

Topic starter 28/05/2026 9:20 pm

That's fantastic news, it was good old AI that said coal fired back boilers are not covered, I then looked on a few other sites and was unable to find coal fired back boilers listed in any of the qualifying criteria.

I am in North Essex, I was contemplating Octopus doing the installation, I did speak to them briefly several months ago but they seemed to suggest they would not do the install during the build, I would need to complete the build first, this seemed odd to me as would almost be a retrofit in a new build!?! I have also since read a few negative reviews of their cozy pumps.

Would you happen to have a list of recommended installers for the CO12 postcode area please?

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Judith

(@judith)

Prominent Member Member

Joined: 3 years ago

Posts: 528

28/05/2026 9:28 pm

@phleach welcome to the forum and what a lovely project to have. To ensure your ufh can be run at the lowest temperature you should get your plumber to design the uf pipework with a gap of 100mm. Our plumber assured us that 250mm was OK and I was so pleased I could find different information because otherwise we would have needed supplementary heating in those rooms.

2kW + Growatt & 4kW +Sunnyboy PV on south-facing roof Solar thermal. 9.5kWh Givenergy battery with AC3. MVHR. Vaillant 7kW ASHP (very pleased with SCOP >4) open system operating on WC

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