If you search online how domestic heat pumps work, you soon find out that they are expensive to install and generate a constant noise that could be a problem with close neighbours (£5,000 grants unveiled to support home heat pump installation, 18 October). What is less well known is that, although they might replace what gas and oil-fired domestic boiler systems do, they also start becoming less efficient and effective when the outside temperature is about 5C and lower – just the temperature at which you definitely need effective domestic heating.

Also, there is no guarantee that the electricity used to power each unit comes from a renewable or truly zero carbon source. So why are we wasting our time with this “compromise”, and at a cost to us taxpayers of £5,000 a pop? Surely it couldn’t be for last minute Cop26 cosmetic reasons?

Gary Bennett

Exeter

The government has in effect asked us, over the next 30 years, to change our gas boilers for ground or air source heat pumps. For some people this is an acceptable technique. But for many, particularly those in high-rise buildings, this is impractical due to the difficulties in attaching the units to the outside of a tall structure.

A better and much cheaper solution for those people is to use the existing natural gas system to supply green or blue hydrogen. At worst, they may have to replace their boilers, but hopefully only the burners and meters, as was done when we changed from town gas to natural at the end of the 1960s.

Frank Brown

London

There can be little doubt about the necessity of moving to more sustainable sources of domestic energy. However, air source heat pumps would require most older homes to be retrofitted with significant extra insulation and, in replacing combi-boilers, the installation of hot water storage systems, possibly with additional electric heating to cope with higher temperature demands.

It is putting the cart before the horse to offer grants for heating systems before getting our houses in order through realistic funding of the insulation and adaptation of current systems.

Austen Lynch

Garstang, Lancashire