One of the most important things to do when installing a heat pump at home is to have your radiators upgraded for larger or more efficient radiators. Heat pumps are designed to keep a constant temperature by heating the water which runs through your radiators 20% to 40% cooler than what gas and oil boilers are traditionally run at, this is know as the flow temperature, however by heating over a longer period of time with bigger radiators that let more heat out into the rooms, then you can achieve the same or sometimes more heat than what you had before. It is strongly recommended not to cut corners on radiators, in fact it is so important that all MCS accredited installers need to follow strict rules to calculate and fit the right size radiators, or they risk their accreditation status being reversed.