Battery Combi Boilers UK: Luthmore Review

Most low-carbon heating advice in the UK boils down to two options: a gas boiler you keep, or a heat pump you commit to. A battery combi boiler is a newer third category — a wall-mounted electric unit that stores electricity in an internal battery, then discharges it at high power to deliver gas-boiler-style hot water and heating on demand. The best-known UK example is Luthmore, built by a team of ex-Dyson engineers. This guide explains how the technology works, what it costs, and where it fits against the heat pumps and hybrid systems we've covered elsewhere on this site.

What is a battery combi boiler?

A battery combi boiler charges an internal battery pack from the electricity grid or a solar array, then releases that stored energy in short, high-power bursts to heat water instantly — the way a gas combi does, but without gas. Ordinary electric boilers are capped by the size of your household electrical supply, which is why most only manage around 10kW and struggle to match a gas combi's instant hot water. A battery buffer removes that ceiling: the unit can draw a large burst of stored power for a few minutes at a time without tripping the property's electrical supply.

Luthmore's system, according to the manufacturer's own product information, stores energy in lithium iron phosphate (LFP) batteries — the same non-rare-earth chemistry increasingly used in UK home battery storage — and can charge from the grid at off-peak rates or directly from a home solar PV system. The unit fits the same cupboard space as a standard combi boiler and connects to existing pipework, so there's no hot water tank and, unlike a heat pump, no outdoor unit.

How Luthmore's system performs

Independent reporting on Luthmore's specification puts the battery capacity at around 5.9kWh, with a further 1.2kWh recovered through a patented waste-heat recovery system that captures heat generated during charging and discharging — adding roughly 15% more usable energy without extra battery cells, according to Electric Home's coverage of the launch. On output, the unit delivers hot water at up to a 30kW-equivalent burst — in the same range as a mid-size gas combi — and around 10kW for central heating, which independent reviewers note is drawn more directly from mains electricity than from the battery, so the efficiency gains are stronger on hot water than on space heating (Heatable's independent review).

That's a meaningful distinction if you're weighing this against a hybrid heat pump: a hybrid system genuinely offloads a large share of your heating load onto a more efficient heat pump for most of the year, while a battery combi boiler's main advantage is shifting when you draw grid electricity, plus giving your solar panels somewhere useful to send power on days you're not heating water. It doesn't improve the underlying efficiency of turning electricity into heat the way a heat pump's coefficient of performance does.

What does a battery combi boiler cost?

Luthmore's unit price is reported at around £4,500 plus VAT, with installed pricing from third-party installers starting from roughly £6,500 once removal of the old boiler and connection work are included — figures should be confirmed directly with an installer, as retail pricing on a newly launched product moves quickly. For comparison, our heat pump vs gas boiler cost guide puts a combi boiler swap at £2,000–£3,500 and a full air source heat pump at £9,000–£14,000 before grants, so a battery combi boiler currently sits in between — closer to a hybrid heat pump's installed cost than to a like-for-like gas boiler.

The company itself, founded by Craig Wilkinson and Martin Gutkowski, has raised £6.9 million in funding and is currently running trials with Oxford University and social landlords while shifting production toward contract manufacturing, per Electric Home's reporting. That's worth flagging for anyone comparing this to established boiler or heat pump brands: it's an early-stage product from a well-funded but young company, not a decade-proven appliance.

Does it qualify for the Boiler Upgrade Scheme?

No — battery combi boilers do not currently qualify for the £7,500 Boiler Upgrade Scheme (BUS) grant. BUS funding is restricted to MCS-certified air source and ground source heat pumps (and biomass boilers in off-gas areas); a battery-buffered electric boiler doesn't meet that definition, regardless of its efficiency claims. Heatable's review notes there is industry hope that products in this category could eventually be brought into an expanded scheme, but homeowners should treat that as a future possibility, not a current entitlement. If accessing the BUS grant matters to your decision, our hybrid heat pump guide explains which systems are and aren't eligible today.

Solar and battery combi boilers

The strongest fit for this technology is a home that already has — or is planning — solar panels. Because the unit charges from any electricity source, surplus solar generation during the day can top up the boiler's battery instead of exporting to the grid at a low Smart Export Guarantee rate, then that stored energy heats water on demand into the evening. It's the same self-consumption logic behind a standard home battery, covered in our are solar batteries worth it guide — a battery combi boiler is effectively a smaller, heating-dedicated version of that idea, rather than a replacement for whole-home battery storage.

It also suits time-of-use electricity tariffs: charging the battery overnight on a cheap rate (in the way home battery storage systems already do) avoids paying peak-rate electricity for hot water, even without solar panels on the roof.

Who should consider one?

A battery combi boiler is worth investigating if you:

• Have solar panels or a time-of-use tariff and want to shift more heating-related electricity use to cheap or self-generated power.
• Want gas-boiler-style instant hot water without ripping out radiators or finding space for an outdoor heat pump unit.
• Are comfortable trialling an early-stage product from a newer manufacturer rather than an established brand.

It's probably not the right fit if you need the BUS grant to make the numbers work, or if space heating — not hot water — is your main cost concern, since independent reviews suggest the heating side draws more directly from mains electricity with less of the battery-buffered advantage. For most UK homes focused purely on cutting heating bills and carbon, a standalone heat pump or hybrid system remains the more established route; see our heat pump vs gas boiler comparison for the fuller cost breakdown.