The Government has written that a heat pump “generates 3 times more energy than it consumes”.
Evaluation
Heat pumps are highly efficient and can release three times as much heat energy into a home as they consume energy in the form of electricity, but this is not the same as generating three times more energy than they consume.
The facts
Heat pumps work very differently to other sources such as gas-powered boilers or electric heaters.
Gas boilers work by burning gas, with their efficiency measured by the proportion of the energy from that gas which goes into the home in the form of heat, rather than being lost out of the flue. Such a loss is in part due to not all of the gas involved in the process being burnt off.
When installed and calibrated correctly modern gas boilers are very efficient, losing less than a 10th of the energy from the gas they use. However, experts suggest most domestic gas boilers are not given the most efficient settings by the installer. They suggest that homeowners and tenants should check their boilers to see if they could reduce the gas needed, and therefore money.
An A-rated gas boiler which is installed correctly has an efficiency of 90% or more.
Electric heaters, on the other hand, are 100% efficient. They work by turning energy from electricity into heat energy.
When other electrical appliances – such as light bulbs – are given an efficiency rating, it measures the proportion of the electrical energy which is used to carry out the task, such as producing light.
All the remaining energy from the electricity is “lost” as heat.
For example, traditional incandescent light bulbs only converted 5% of the energy in the electricity they used into light, with the remaining 95% being released as heat. But because electric heaters are designed to produce only heat, there is no waste by-product, so they are all considered 100% efficient.
Heat pumps work very differently to traditional heating. Rather than converting electrical energy to heat energy which is released into the home, they instead use electricity to move heat energy from outside into the home.
This is done by compressing a refrigerant which absorbs heat energy from outside and then releases it inside. It is the same method used for an air conditioning unit to cool a room, but in reverse.
For every unit of energy consumed, heat pumps can release several times that amount in heat in a home. This is not always three times the electric input; it can be more or less depending on a series of factors.
Links
The Heating Hub – Boiler efficiency calculator (archived)
Energy Saving Trust – Boiler types explained (archived)
Trust – Why is Electric Heating 100% Efficient? (archived)
