By the UK Wood Gasifier Hub – Off-Grid Power & Biomass Energy Guides Team · Updated May 2026 · Independent, reader-supported

Using a Wood Gasifier for Combined Heat and Power (CHP) UK: Is It Worth It?

Combined heat and power—sometimes called cogeneration—is an approach that captures the waste heat from electricity generation to warm your home and water. For anyone running a wood gasifier, it's worth understanding whether the added complexity and cost actually delivers results in the UK climate. The short answer: it can work very well, but only under specific conditions.

How CHP Works with Wood Gasifiers

A wood gasifier generates electricity through a small generator (typically 5–15 kW for domestic systems). The exhaust gases from the engine powering that generator emerge at 200–400°C. In a standard setup, that heat goes straight into the air. In a CHP system, you capture it.

A heat exchanger—usually a plate or shell-and-tube type—sits in the exhaust stream. Water or thermal fluid flows through it, absorbing that heat and transferring it into a thermal store (large insulated tank) or directly into your heating system. This heat then serves two purposes: space heating via radiators or underfloor heating, and pre-heating domestic hot water (DHW).

The gain is real. A gasifier-generator combination might operate at 35–40% electrical efficiency. Without heat recovery, the remaining 60–65% is wasted. With proper CHP integration, you can capture 50–70% of that waste heat. That's a significant uplift to overall system efficiency.

Real-World Efficiency Figures

Lab-rated figures often claim total system efficiencies of 75–85%. In practice, UK installations see 60–75% overall efficiency—still well ahead of grid electricity plus a boiler running separately, provided you're using the heat.

The critical dependency is load matching. A gasifier running continuously in summer to charge a battery bank produces far more heat than you need; much of it will be rejected. In winter, when you're heating space and water anyway, that same heat is gold. The seasons matter.

A 10 kW electrical gasifier running at full load produces roughly 15–20 kW of recoverable waste heat. A three-bedroom UK home using 12,000 kWh of heating annually (space heating plus DHW) is drawing about 3.8 kW average. If your gasifier runs 8 hours daily, that's 30 kWh of heat daily in theory—but your home needs perhaps 3–5 kWh on average (higher in winter, lower in spring). The mismatch demands good thermal storage: a 2,000–5,000 litre tank to bank heat from high-output periods into low-demand periods.

The Infrastructure: Thermal Storage and System Layout

Installing CHP properly means investing in a thermal store—a large, well-insulated tank that acts as a buffer. This tank sits between the heat recovery exchanger and your heating circuits. It smooths out the timing mismatch between when the gasifier generates heat and when your home needs it.

From the store, you draw heat for space heating (via a mixing valve to the correct flow temperature) and for DHW (either via immersion coils in the store itself, or a plate heat exchanger for on-demand heating). Good stratification—keeping hot water at the top and cooler return water at the bottom—matters; it maximises usable heat.

For DHW alone, if you size a coil inside the tank correctly, a 3,000 litre store can supply 30–50 litres of DHW at 60°C daily per kWh of heat stored. In practice, if your gasifier delivers 15 kWh of heat on a winter day and your home uses 4 kWh for heating and 2–3 kWh for DHW, you're storing the surplus. That works. In summer, if you're only running the gasifier for electricity and generating excess heat, a secondary rejection circuit (an air-cooled radiator outdoors) prevents temperature creep in the tank.

When CHP Makes Sense

CHP is worthwhile if:

• You're already committed to a wood gasifier for year-round electricity and have adequate timber supply
• Your home needs genuine heating load in winter – a well-insulated building or one in a colder part of the UK
• You have capital for a thermal store and good pipework – this isn't a cheap retrofit
• You're off-grid or in a high-cost grid area where the electricity displacement value is high
• You're willing to manage the system actively—checking temperatures, managing rejection, understanding how it performs

When It Doesn't

CHP adds cost and complexity for limited gain if:

• You're in a mild southern climate with low winter heating demand
• Your gasifier is undersized or runs intermittently; a 3 kW gasifier produces modest heat
• You have limited space for a large thermal store
• You're grid-connected with cheap electricity; the electricity alone is less valuable
• Your home is already heated by mains gas and you're only adding the gasifier for backup—the case for CHP weakens

The Real Costs

A CHP-capable system costs £2,000–£4,000 more than a basic gasifier setup (heat exchanger, controls, piping, insulation). A thermal store runs £3,000–£8,000 depending on size and quality. Installation labour for plumbing and controls can be £2,000–£4,000. Over 15–20 years, that capital is worth the return only if the heat is genuinely used—and if timber costs remain reasonable.

Verdict

CHP with a wood gasifier works well in the UK when you have serious winter heating needs, good site conditions for timber, and are willing to invest in proper thermal infrastructure. It transforms a gasifier from an electricity-focused system into a genuine wholehouse energy solution, with total efficiency figures that rival modern heat pumps when you include the displaced grid electricity.

For a small rural property with significant heating demand and poor grid connections, it's a serious contender. For a terraced suburban home, it's unlikely to justify the cost and complexity. Assess your actual winter heat demand first.