Heat pumps don't generate heat like when you burn gas. Instead, they capture heat from the air (in the case of an air source pump), and move it into your house. That is why heat pumps have the strange property of being more than 100% efficient – for every unit of electricity you put in, you capture and concentrate about 3 or more units of heat from the outside. This means that heat pumps don’t just let us use clean renewable electricity rather than burning fossil gas. They also reduce the total amount of energy we need to put into heating our homes by around 3-4 times. Nice!