I remember as a student putting a shilling (2.5p) in the meter to run one bar of an electric fire for an hour to heat my single room. The heat was soon lost again due to poor insulation.
I now live in a large house heated to a steady 21C by an air source heat pump that uses less energy per hour than the one bar fire did to heat a single room, even in cold weather. It also heats water twice a day to 55C.
Our heat pump works by extracting heat from the air outside and using it to heat water, which then circulates through the underfloor heating system. This works well because the floor area radiating heat is much larger than traditional radiators, so the circulating water does not need to be as hot as in a conventional system. The key point is that the electrical energy needed to run the pump is much lower than the heat energy it provides.
Many households will need to replace their gas or oil boilers with heat pumps if we are to have any chance of reaching the government’s net zero carbon target by 2050. Heating accounted for nearly one third of UK household greenhouse gas emissions in 2017, according to the Energy Saving Trust. We need to cut heating emissions by 95% to reach net zero by 2050, it says.
So far we have made little progress. Currently, biomass is the main source of low emission heat in British homes, primarily supplied via wood burning stoves. Around 1 million homes make use of this energy source, according to the Climate Change Committee, which advises the UK government. Heat pumps account for fewer than one in 100 sales a year of heating systems and show little sign of becoming more popular.
Part of the problem is that heat pumps work best in houses that are well insulated and airtight. That makes them a good choice for new build houses. My house, for example, was built 10 years ago and designed for maximum energy efficiency. It is an oak framed building with insulated wall and roof panels, underfloor insulation and triple glazed windows. Plus solar panels and the heat pump. It has an Energy Performance Certificate rating of A and is as airtight as possible while still being well ventilated.
Installations in older buildings are possible but it is important to obtain a professional whole house heat loss calculation so that the heat pump and radiators or underfloor heating are correctly sized. If this is not done a heat pump may not work well.
It is likely you will have to improve your home’s insulation before you can install a heat pump, but this is an investment worth making however you decide to heat your home. It will reduce your energy use, which is the first step to decarbonising your home.