Ceredigion had one of the highest rates of heat pump installations in the UK, figures suggest.
Industry bodies and pressure groups have warned the UK Government is already lagging behind its target, as Prime Minister Rishi Sunak rolled back various green pledges.
Figures from MCS, the standards body for heat pumps and other energy-saving technology, suggest 1,486 heat pumps were installed in Ceredigion from 2009 to September – covering an estimated 4.3 per cent of households in the area, and one of the highest rates in the UK.
Heat pumps work by extracting heat from the air or the ground outside and pumping it into a building, operating like an air conditioner in reverse. They are more energy efficient than traditional boilers, and the government has been providing grants to encourage households to upgrade.
MCS' figures cover most installations across the UK.
The government has pledged to install 600,000 heat pumps a year by 2028 – MCS figures show there were fewer than 33,000 installed last year, although separate industry figures show around 55,000 heat pumps were sold across the UK in 2022.
An MCS spokesperson said they welcomed the government's decision to increase grants for heat pumps from £5,000 to £7,000, but warned uptake would need to increase "exponentially" to meet the government's target.
Across the UK fewer than 26,000 have been installed so far this year – with 434 of them in Ceredigion homes, 627 in Powys and 423 in Gwynedd.
As part of Thursday's announcement, Mr Sunak promised to roll back demands on landlords to improve the energy efficiency of lets and upgrade old boilers.
But analysis suggests private renters are already the least likely group to have had a key energy efficiency upgrade, such as a heat pump or solar panel.
Across the UK, owner-occupied homes are nearly 50 per cent more likely to have had one of these energy-saving measures installed.
In Wales, there have been 34 installations for every 1,000 owner-occupied homes, compared to 24 in 1,000 for private tenant households.
Greenpeace UK’s climate campaigner Georgia Whitaker called the announcement "bad news" for private renters, who are already suffering the worst of the cost-of-living crisis.
She added: "The pledge to “never” increase energy efficiency standards for the private rented sector will be worrying thousands, as they remember just how cold they were last winter in badly insulated homes."
The Energy Saving Trust, which also campaigns for energy efficiency, said it was disappointed at the news.
Stew Horne, head of policy at the organisation, said: "As the climate emergency escalates, now is the time for scaling up ambition and action to provide industry and public confidence and bring down costs.
"Now is not the time to backtrack on targets and risk being left behind whilst the rest of the world is making the just transition to net zero."
A spokesperson for the Department for Energy Security and Net Zero said: "We’re investing billions to improve energy efficiency across the country, supporting households switch to low-carbon alternative heating."
"We are supporting property owners and landlords to switch through schemes like the Boiler Upgrade Scheme – which has now received a 50 per cent increase in funding from £5,000 to £7,500 – making it one of the most generous support schemes of its kind in Europe," they added.