Ken Read MCIAT offers a reality check for headlines that eulogise air source heat pumps in the battle against climate change.
An article about banning gas boilers, appeared in the Mail Online, on Wednesday 26 May 2021, it stated in relation to air source heat pumps, (costing £11,000 to install).
“A typical three-bedroom home is said to be able to save £2,755 in ten years by using this instead of a gas boiler.”
This is statement is absurd, untrue and totally incorrect.
An air source heat pump does not produce heat, it only transports it, concentrates it and releases it inside a building, working similarly to a refrigerator.
The efficiency of a heat pump is quoted as a Coefficient of Performance (CoP), because it is not actually producing the heat. A typical heat pump will have a CoP of 3 or 4 which is equivalent to 300% or 400% efficiency of a boiler producing heat, usually CoP 4 is in summer and CoP 3 in winter, as the lower external temperature makes it more difficult to transport and concentrate the heat.
A current condensing gas boiler has an efficiency rating of approximately 95%. On those initial figures it would appear a heat pump is three to four times more efficient than a condensing gas boiler.
Unfortunately, this is only part of the story. Currently gas prices are about 3.2 pence per Kwh and electricity is about 18 pence per Kwh (Octopus tariff prices). This means that an electric heat pump is 18/3.2 = 5.625 times more expensive to run than a gas boiler, a heat pump’s winter efficiency is 300/95 = 3.16 times more efficient, therefore to run a heat pump is 5.625/3.16 = 1.78 times more expensive in true economic terms.
“An air source heat pump will never make a saving at current gas and electric prices, in fact it will cost nearly twice as much.”
It will never make a saving at current gas and electric prices, in fact it will cost nearly twice as much. This is particularly true when considering that the heat produced by a heat pump is usually of lower temperature than that which can be produced by a gas boiler, requiring either underfloor heating or enlarged radiators to effectively heat a premises.
When considering global warming, additional factors other than economics are relevant. Electricity is supposedly green and burning gas as a fossil fuel is bad for the environment, however the carbon cost of electricity production is only less than gas production if the electricity comes from eco-friendly resources such as solar, wind or hydropower.
Solar power is in abundance in summer months, when least heating is required and the opportunities for hydropower in the UK are very limited. It would therefore be necessary to produce all electricity by wind power during winter months to maintain a reduction in carbon emissions. Other calls on green electricity, such as EVs , trains, industry, increase the usage of this resource in winter, in addition to the normal lighting and power demands of domestic accommodation.
No account in this narrative has been taken of the production carbon cost of the unit itself. The price quoted of £11,000 for a heat pump compares unfavourably with the average cost of £2,000-£3,000 for a gas boiler installation, belying the more complicated installation and expense of equipment construction, which is not conducive to reducing a carbon footprint
Don’t get me wrong, I am an avid supporter of the fight against global warming, but it must be done intelligently and not to satisfy political deadlines or electoral pledges, when the facts and figures used to justify the action are fundamentally flawed.