A combined heat and power (CHP) unit generates heat and electricity at the same time with around 90% overall efficiency (60% heat, 30% electricity). Unlike energy generated by a plant which is largely wasted, a CHP unit uses up any ‘waste’ heat captured, making it more efficient than electric off the grid or gas from the mains. And having a CHP unit means you’re eligible for an Enhanced Capital Allowance and Climate Change Levy exemption. Winner, winner.