What the grant requires
Earlier versions of the Boiler Upgrade Scheme carried an insulation condition. It was removed on 8 May 2024, and a further rule change on 28 April 2026 relaxed the EPC requirement: the installer provides the EPC reference if one exists, otherwise other evidence. Today the test is about the property type, the owner, the heating being replaced and the installer, not insulation. The eligibility page sets out every test, and you can answer six questions in the checker below without giving contact details.
Which grant would apply to you?
Six quick answers; contact details are optional and only needed if you want us to reply by email. Indicative only — your MCS installer checks eligibility and Ofgem makes the decision.
Likely £7,500
Owner-occupied home in England on mains gas replacing the boiler with an air-to-water heat pump.
Rules: GOV.UK “Apply for the Boiler Upgrade Scheme” and Ofgem’s property owner guidance (v5.1). Grant bands from the notice of grant categories updated 21 July 2026.
The band that applies is £7,500 for an air source or ground source heat pump, or £9,000 where the home has no mains gas and replaces oil or LPG heating. Installers apply on your behalf; see the how-to-apply guide.
What the evidence says
The Energy Saving Trust is clear that you do not need lots of insulation to have a heat pump, but that, like any heating system, heat pumps work best in a well-insulated home. The Energy Systems Catapult trial gives the practical picture. Energy-efficiency upgrades were installed at 15% of properties, mostly loft insulation with a few cavity wall insulation or door replacements. Many properties already had suitable loft and wall insulation, and 94 heat pump systems went into properties with no, or unknown, wall insulation because designers and installers considered them suitably energy efficient (54 of these were low temperature units, per the Summary Report). The trial also reported no significant difference in ashp spf by house type or age.
That does not say insulation is irrelevant. It says the decision is made house by house on the heat-loss calculation, not by a blanket rule.
How insulation changes the design
| If the house loses less heat | Result |
|---|---|
| Heat demand falls | The heat pump can be smaller, and the electricity it uses falls with it. |
| Radiators can be smaller | Fewer radiators need upsizing, which reduces cost and disruption. |
| Flow temperature can be lower | The system runs at a more efficient point (see the efficiency guide). |
| Rooms warm more steadily | The Energy Saving Trust says good insulation keeps the home warm for longer so the heat pump works less. |
This is the same logic in reverse for a poorly insulated house: it needs a larger heat output and so larger radiators, which is why the survey calculation matters. The sizing guide covers the mechanics.
Before, after or never?
The Energy Saving Trust advises finishing planned insulation work before the heat pump is fitted so the system heats all of your home adequately from day one. In practice that gives three routes:
- Insulate first if the work is cheap, quick and planned anyway, such as loft top-up. Ask the installer to size the heat pump for the improved house, and say so in writing.
- Do both at once if you are renovating. The installer can design for the finished fabric.
- Proceed without if insulation is impractical or unaffordable, and accept a bigger design. This is common in older homes; the old houses guide covers what to expect.
A caution on sizing: if you plan improvements later, tell the installer now. A heat pump sized for today’s heat loss will be oversized once the house is better insulated, which the installer needs to weigh against comfort in the meantime.
If you cannot insulate
The Trust’s advice for an older home with little or no insulation is to design around it: likely bigger radiators throughout and possibly an extra one here and there, and to say yes if the installer offers upgrades, to avoid unwelcome fuel bill surprises. Run the heating steadily at a constant level, bring it on earlier in the morning, and, if the house is empty during the day, turn it down rather than off. Do not worry if radiators do not feel very hot, because they will still heat the room if left on long enough. The controls guide explains those settings.
Funding for insulation sits outside the heat pump grant. The Great British Insulation Scheme, once a common route, ended on 31 March 2026. ECO4 runs until 31 December 2026, and the Warm Homes: Local Grant is council-run in England for low-income households; both are set out in other funding routes. Check the scheme’s own page before you count on it.