Stop throwing away two thirds of your fuel.

The basic idea

Any combustion engine wastes most of its fuel as heat — through the exhaust, the cooling system and the oil. A generator running on its own dumps all of that to atmosphere.

Combined heat and power recovers it. The same engine produces electricity as before, and heat exchangers capture the rest into a hot water circuit for space heating, hot water or process heat.

Where the fuel goes	Generator alone	With heat recovery
Electricity	~30–35%	~30–35%
Useful heat	Nothing — all lost	~45–55%
Total useful output	~30–35%	~80–90%

Indicative figures for small-scale reciprocating engine CHP. Actual performance depends on the engine, the recovery system and how much of the heat you genuinely use.

The condition that decides everything

Where it does line up

• Off-grid homes running a generator anyway. If the engine has to run in winter to charge the battery, and winter is exactly when you want heat, the two demands coincide almost perfectly. This is the strongest domestic case there is.
• Properties with a swimming pool — a large, constant, year-round heat load, which is otherwise expensive to serve off-grid.
• Farms and rural businesses with process heat: grain drying, dairy hot water, glasshouses, digestate warming.
• Buildings with continuous hot water demand — care settings, some hospitality, anywhere with a constant draw.

Why off-grid is the natural fit

On a grid-connected building, CHP competes against buying electricity, which is usually cheap and always available. The case has to be made on price alone and it is often marginal.

Off-grid, the comparison is entirely different. You are generating anyway. The engine is running anyway. The fuel is being burnt anyway. Recovering the heat is close to free energy — and it displaces whatever else you would have used to heat the building, which off-grid is usually expensive.

For an off-grid property in the North East with a genuine winter heat demand, CHP can be the difference between a system that works and one that constantly disappoints.

Fuel

• Natural gas — cleanest and simplest, where a mains supply exists. Off-grid for electricity does not necessarily mean off-grid for gas.
• LPG — the usual answer for genuinely remote properties. Bulk tank, stores indefinitely, burns cleanly.
• Diesel — workable and often the cheapest engine, but dirtier and noisier, which matters more when the unit is running regularly rather than occasionally.
• Biogas or biomass — for agricultural sites with a feedstock, a different scale of project but a real one.

What a scheme involves

1. Heat and power demand assessment. Both, hour by hour through the year. This is the work that determines whether the scheme is worth doing.
2. Sizing. Almost always to the heat demand rather than the electrical one, with the battery covering electrical peaks.
3. Integration with the heating system — thermal store, controls, and what happens when heat demand disappears.
4. Installation and commissioning, electrical and mechanical.
5. Monitoring, so you can see how much heat is genuinely being used rather than assumed.