Put very simply a renewable heating system is one that produces more heat than it uses to produce that heat. If you are using a conventional gas boiler then at best it will be running at 95% efficiency – so every 1 Kw of power used will only produce 0.95 Kw of heat. If your boiler is getting on a bit then this efficiency will decrease. Renewable system can work on a ratio of 1:4 – every 1 Kw of power could produce 4 kw of heat, as a minimum it will produce 2.5 Kw. It sounds like magic but air source and ground source heat pumps have been producing these results for decades and as gas prices continue to climb then this has to be the way forward.