Homeowners in England and Wales will be offered subsidies of £5,000 from next April to help them to replace old gas boilers with low-carbon heat pumps.

The grants are part of the government's £3.9bn plan to reduce carbon emissions from heating homes and other buildings.

It is hoped no new gas boilers will be sold after 2035. The funding also aims to make social housing and public buildings more energy-efficient. But experts say the budget is too low and the strategy is not ambitious enough.

Mike Childs, head of science at Friends of the Earth, said the number of heat pumps that the grants would cover "just isn't very much" and meant the UK would not meet its aim of installing 600,000 heat pumps a year by 2028.

Heat pumps extract warmth from the air, the ground or water - a bit like a fridge operating in reverse. They are powered by electricity, so if you have a low-carbon source of electricity, they provide greener heating.

The UK has committed to reducing its greenhouse gas emissions to net-zero by 2050. Heating buildings accounts for more than a fifth of the UK's overall greenhouse gas emissions, so there is pressure on the government's Heat and Buildings Strategy to deliver effective reductions.

Business and Energy Secretary Kwasi Kwarteng said the grants to support the adoption of heat pumps, available from next April, would help to bring down the cost of the relatively new technology by 2030.

An air-source heat pump costs between £6,000 and £18,000, depending on the type installed and the size of a property.

While homeowners will be encouraged to switch to a heat pump or other low-carbon technology when their current boiler needs replacing, there is no requirement to remove boilers that are still working, the government emphasised.

One energy firm, Octopus Energy, said it expected homeowners to pay about £2,500 to the cost of installing a heat pump, roughly equivalent to the cost of a new gas boiler. The government subsidy would cover the rest.

But many houses will require an upgrade to their energy efficiency, including insulation, before installing one.

Information sourced from BBC.