Heat pumps take energy from the air or ground and transfer it into water circulating through your heating system. The running costs for a well designed and specified heat pump should be comparable to operating a natural gas boiler. The government’s RHI scheme pays you several thousand pounds over seven years to offset the installation cost.
Heat pumps operate most efficiently when paired with underfloor heating. Radiators need to be oversized or have forced ventilation. If you can’t change your existing radiator system, you could have a high temperature heat pump or you could consider a hybrid system, which retains your existing boiler.