TL;DR:

  • Micro-CHP units use a Stirling engine to generate electricity while heating your home — the heat is the primary output, electricity is a bonus
  • The main product available in the UK is the Baxi Ecogen (formerly Remeha); it replaces your gas boiler and generates up to 1 kWe of electricity
  • The economics depend heavily on how much of the electricity you use on-site — self-consumption is key; the technology makes more sense in high-heat-demand homes than in low-demand ones

Combined heat and power — CHP — has been used at industrial and commercial scale for decades. The idea is straightforward: instead of letting the heat produced by electricity generation go to waste (which is what happens in a conventional power station), you capture it and use it for heating. The result is a much more efficient use of the fuel.

Micro-CHP applies the same principle at domestic scale. You install a unit that replaces your gas boiler, and instead of just burning gas to heat water, it also generates a small amount of electricity in the process. It’s not a renewable technology — it still burns gas — but it can be meaningfully more efficient than a conventional boiler, and it produces electricity that reduces your grid draw.

The question is whether it makes sense for a UK home in 2026.

How Stirling Engine Micro-CHP Works

The most common technology used in domestic micro-CHP is the Stirling engine. This is a type of heat engine that works by the cyclical compression and expansion of a sealed gas (usually helium or hydrogen) as it moves between hot and cold regions.

In a micro-CHP unit, the burner provides the hot side of the Stirling engine. As the gas inside the engine expands and contracts, it drives a linear alternator — generating electricity. The heat that would otherwise be waste is transferred to your central heating and hot water system.

This is importantly different from a heat pump: a heat pump uses electricity to move heat from outside into your home. A Stirling micro-CHP unit burns gas and uses the combustion energy for both heating and electricity generation simultaneously.

What’s Actually Available in the UK

The main micro-CHP product available in the UK residential market is the Baxi Ecogen 1.0e (previously sold under the Remeha brand). It’s a wall-hung unit roughly the size of a conventional combi boiler, with a heat output of up to 24 kW and an electrical output of up to 1 kWe.

That 1 kW of electricity might sound modest — and it is. On a cold day when the unit runs continuously, it might generate 8–10 kWh of electricity. On a mild day when it only fires occasionally, it might generate 2–3 kWh. Annual generation for a well-matched installation is typically in the 2,000–4,000 kWh range.

By comparison, a 4 kWp solar panel array in the UK might generate 3,500 kWh per year. Micro-CHP isn’t a replacement for solar, and it produces electricity in winter (when heating demand is high) rather than summer (when solar peaks).

The Economics in 2026

The economics are better than they were five years ago, largely because grid electricity prices have risen substantially. Self-consuming electricity you generate — instead of buying it from the grid at prevailing rates — is where the value comes from.

If you self-consume 70% of your generation at a rate of 28p/kWh, and export the rest under the Smart Export Guarantee (currently paying 4–15p/kWh depending on your supplier), the annual electricity value from a well-used Ecogen might be £600–900.

The installation cost for a micro-CHP unit is typically £3,000–5,000 installed, which is meaningfully more than a standard combi boiler (£2,000–3,000 installed). The Baxi Ecogen also has higher maintenance requirements than a conventional boiler due to the Stirling engine components.

Simple payback — ignoring maintenance costs — is roughly five to ten years in homes with high, consistent heating demand. In homes with low heating demand (well-insulated modern properties, or homes that have already installed heat pumps for part of their heating), the economics become less attractive because the unit generates less electricity when it runs less.

Who It Actually Makes Sense For

Micro-CHP is best suited to:

Older, less well-insulated properties with high and consistent heating demand. These homes run their boilers frequently through winter, which means the Stirling engine runs frequently and generates more electricity.

Homes with high daytime electricity consumption that can use the generated electricity on-site. A home where someone works from home all day, running computers and other equipment, benefits more from on-site generation than a home that’s empty until evening.

Homes not suited to heat pumps for practical or planning reasons. Heat pumps are the preferred low-carbon direction of travel, but properties without space for external units, or in conservation areas with restrictions, may find micro-CHP a more practical option.

The Heat Pump Alternative

It’s hard to discuss micro-CHP in 2026 without addressing heat pumps. The government’s preferred trajectory for home heating decarbonisation runs through heat pumps, not gas CHP. A heat pump doesn’t burn gas at all — it uses electricity to achieve heating efficiencies of 2.5–4x what a gas boiler achieves per unit of energy input.

If your home is a reasonable candidate for a heat pump (adequate insulation, space for external unit, appropriate radiators or underfloor heating), a heat pump will typically deliver lower carbon emissions and better long-term economics than micro-CHP, particularly if your electricity is increasingly grid-supplied renewables.

Micro-CHP is a technology that makes genuine sense for a specific subset of UK homes. It’s not a mainstream choice, and it’s not a path to decarbonisation — it still burns gas. But for the right property, replacing an ageing gas boiler with a unit that also generates useful electricity is a pragmatic efficiency improvement.