Extending with energy in mind: heat pump, solar-ready roof, lower bills
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Short answer: the cheapest moment to make a house heat pump ready, solar ready and EV ready is while it is already a building site. An extension changes your home's heat load, its roof area and its electrical demand, so designing energy in from the first drawing costs a fraction of retrofitting it later and avoids paying twice for the same disruption. This is the point of using a builder with an accredited energy company inside it: both sides of the design happen at the same desk.
Fabric first, because the best kilowatt is the one you never need
Insulation and airtightness in the new fabric are designed before any heating is sized. A well-insulated extension can lower the whole house's heat demand per square metre, which is exactly what a heat pump wants: modest, steady heat through generously sized emitters at low flow temperatures.
Design the heat pump in, even if it comes later
- Size radiators or underfloor heating for low flow temperatures now, while floors are up and walls are open
- Route pipework and allow cylinder space at design stage, so the future swap is a weekend not a refit
- If the boiler is due anyway, the extension is the natural moment: the government's Boiler Upgrade Scheme currently offers £7,500 towards an air source heat pump, and our grant guide covers eligibility and process
Weighing up an extension with energy in the mix? A free consultation covers both sides of the design, with no obligation.
Book a Free ConsultationA solar-ready roof is a design choice, not an accessory
Orientation, pitch, structural allowance for panel loads and a duct for cables decide whether solar is easy or ugly. We design new roofs with panel layout in mind; the solar team then installs on a roof that was expecting them. Battery location and cable routes are planned the same way.
EV charging while the walls are open
A supply route to the parking spot costs little during a build and appreciably more chased through finished surfaces later. See EV charger installation for what the finished article looks like.
On EPC outcomes. Insulation, low-temperature heating and solar all move an EPC in the right direction, and we design so the fabric and systems support the highest bands rather than block them. We do not promise a specific band on this page; your design pack states what your specification supports.
When this is not what you want to hear
If the budget only stretches to the extension itself, do the enabling work anyway: emitter sizing, cylinder space, cable routes, roof structure. It costs little inside a build and keeps every option open. What we advise against is spending on visible energy kit while skipping the fabric, because no heat pump rescues a leaky building.
Quick answers
Can the £7,500 heat pump grant be used during an extension project?
The Boiler Upgrade Scheme applies to qualifying heat pump installations when replacing fossil fuel heating; the building work around it does not change the grant. Eligibility depends on the property and the work, and our grant guide explains the detail. We confirm what applies in your written quote.
Is it worth fitting solar at the same time as an extension?
If the roof is being built or reworked anyway, the marginal cost of doing it now is at its lowest, scaffolding is already up, and the roof can be designed for the panel layout instead of compromised by it. Where budget forces a choice, make the roof solar ready and fit panels later.
Does an extension make my current boiler inadequate?
Sometimes. More volume means more heat demand, and an ageing boiler already at its limit is a poor foundation for a bigger house. The design stage includes a whole-house heating check either way, by our own heating engineers.
Next step: a free consultation on your actual project, or browse the rest of the advice hub.