In short
A gas boiler is usually the simpler like-for-like replacement. An air source heat pump can cut carbon but works at lower flow temperatures, so it may need larger radiators and a hot water cylinder. In England and Wales, GOV.UK's Boiler Upgrade Scheme offers £7,500 towards an air source heat pump through an MCS certified installer.
How are they different?
A gas boiler burns gas to heat water for your radiators and taps, at the higher temperatures most existing radiators were sized for. An air source heat pump takes heat from the outside air and uses electricity to raise it to a useful temperature. It works most efficiently at lower flow temperatures, which is why the rest of the heating system matters so much more with a heat pump.
What changes in my home with a heat pump?
- Radiators: because the water is cooler, some rooms may need larger radiators to stay warm. The Energy Saving Trust advises running a heat pump at the lowest flow temperature that keeps every room comfortable.
- Hot water: a heat pump heats a hot water cylinder rather than giving instant hot water like a combi, so you will need space for one.
- Outdoor unit: an outdoor unit needs a suitable spot outside, with space around it.
- Insulation: the better insulated the home, the easier it is for a heat pump to keep it warm.
What does the Boiler Upgrade Scheme offer?
According to GOV.UK, the Boiler Upgrade Scheme gives £7,500 towards an air source or ground source heat pump in England and Wales. Ofgem says that from 21 July 2026 until 31 March 2027, the grant is £9,000 for air-to-water or ground source heat pumps in off-gas-grid properties replacing oil or LPG heating. You must own the property and be replacing a fossil fuel or electric heating system, the installer must be MCS certified, and hybrid systems that combine a boiler with a heat pump are not eligible. The grant is taken off your installer's quote. Check GOV.UK for the current rules before you rely on it.
When does a gas boiler still make sense?
If your radiators, pipework and space are set up for a combi, and your budget or the house makes a heat pump hard right now, a modern condensing gas boiler is a straightforward replacement. Approved Document L already asks for good controls with a new boiler, and running it at a lower flow temperature where the home stays warm enough helps it condense and use less gas.
What should I ask before deciding?
- What is the heat loss of my home, room by room?
- Which radiators would need replacing for a heat pump?
- Where would the cylinder and outdoor unit go?
- What would each option cost to install, after any grant, and what is included?
- Is the installer MCS certified for the heat pump, and Gas Safe registered for the boiler?
What CombiCert would check
We look at your current heat emitters, insulation, hot-water cylinder space, electrics and how you use the house. That tells you whether a like-for-like gas boiler, a hybrid, or a heat-pump route is realistic for the building, before you spend money on either. Gas boiler work is priced from £1,750 inc VAT subject to a site inspection; heat-pump projects are quoted after a proper survey.
When to call a Gas Safe engineer
Any work on your existing gas boiler, gas pipe or flue, including disconnecting and capping it when a heat pump goes in, must be done by a Gas Safe registered engineer. We are gas engineers, so for a heat pump get a heat loss survey and quote from an MCS certified installer, and compare it fairly with a boiler quote using our quote checklist.
Need a hand? CombiCert in Telford
CombiCert Ltd is a Gas Safe registered (621146) gas and heating company based at The Old School House, Park Lane, Telford TF3 4TG, working across Telford and Shropshire for homes and businesses. We are open Monday to Saturday, 08:00 to 19:45 (closed Sunday).
New boilers from £1,750 inc VAT for a basic like-for-like installation, subject to a site inspection. Most quotes are higher; filters, flushes, thermostats and moving the boiler are paid extras.
See New boiler installation in Telford, or call or WhatsApp 07393 220694, or email hello@combicert.co.uk.
We cover Telford and nearby, including Wellington, Madeley, Dawley, Oakengates, Shifnal, Newport, Ironbridge and Shrewsbury.
Sources
- GOV.UK: Apply for the Boiler Upgrade Scheme, what you can get
- GOV.UK: Apply for the Boiler Upgrade Scheme, check if you're eligible
- Ofgem: Boiler Upgrade Scheme, property owners
- Energy Saving Trust: Air source heat pumps
- Energy Saving Trust: The most efficient way to run a heat pump
- GOV.UK: Approved Document L, Volume 1: Dwellings, 2021 edition incorporating 2023 amendments
Frequently asked questions
How much is the Boiler Upgrade Scheme grant?
GOV.UK says the Boiler Upgrade Scheme gives £7,500 towards an air source or ground source heat pump in England and Wales. Ofgem says off-gas-grid homes replacing oil or LPG can get £9,000 from 21 July 2026 until 31 March 2027. The installer must be MCS certified and claims the grant on your behalf.
Can I get a grant for a new gas boiler?
The Boiler Upgrade Scheme does not fund gas boilers, and hybrid systems combining a boiler with a heat pump are not eligible. Other schemes, such as ECO4, are delivered through energy suppliers for eligible households. Check eligibility on GOV.UK, never pay upfront to a cold caller, and confirm any installer is Gas Safe registered.
Do I need new radiators for a heat pump?
Possibly some of them. A heat pump runs most efficiently at lower flow temperatures, so radiators sized for a gas boiler may be too small to keep some rooms warm. A room-by-room heat loss survey by the heat pump installer will show which radiators, if any, need upgrading.
Can I keep my combi boiler and add a heat pump?
A hybrid system that pairs a boiler with a heat pump is possible, but GOV.UK says hybrid systems are not eligible for the Boiler Upgrade Scheme grant. If you are considering one, get the heat pump side designed by an MCS certified installer, and have any gas work done by a Gas Safe registered engineer.
This answer is general information, not a substitute for an on-site assessment by a Gas Safe registered engineer. If you smell gas, call 0800 111 999.