By Paul Homewood

Following on my post on Northern Powerhomes, it is time to nail the lie that heat pumps are cheaper to run than gas boilers.

A typical detached house with gas central heating would use about 11,000 KWh for heat, and a further 4000 KWh for hot water, according to the Greenmatch website. This is consistent with what I use.

Based on the prices I pay, below, my gas bill should be £370pa. plus £68pa for standing charge. (Currently we have a gas hob, so would still need a gas supply)

According to the Committee on Climate Change’s Sixth Carbon Budget, the average efficiency of air source heat pumps is 300%. (Ground source are slightly more efficient, but are much more costly to install):

An efficiency rating of 300% means that you get 3 KWh of heat for every 1 KWh of electricity input. (See here). The CCC assume by the way that houses are well insulated, as the efficiency rating will be much less otherwise).

Gas boilers are assumed to run at 87% efficiency, so 11,000 KWh of gas produces 9570 KWh of heat. At 300% efficiency, we would therefore need 3190 KWh of electricity.

As electricity costs me 14.49p per KWh, the annual cost would be £462, compared to my gas bill of £271 (excl hot water).

That still leaves the thorny question of hot water. Heat pumps cannot normally raise water temperatures to the level of 60C required to kill legionnaires bacteria. The easiest solution is to install a separate electric water heater, but this would obviously cost more to run than gas.

Alternatively, there are ways to top up the heat provided by a heat pump, known as “hybrid heat pumps”, which would add to the cost of installation. If the hybrid is powered by electricity, we again hit extra running costs. The CCC’s preferred option is to use hydrogen once gas is phased out, but this too is considerably more expensive than natural gas.

Either way, we can expect to see our energy bills rising by at least £300 pa, if heat pumps are installed.

via NOT A LOT OF PEOPLE KNOW THAT

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February 3, 2021 at 06:06AM