Just 221 homes in the city have been fitted with a heat pump in the past 14 years amid warnings of a slow uptake across the UK.
Industry bodies and pressure groups have warned the government is already lagging behind its target, as the Prime Minister rolled back various green pledges.
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.
But despite the grant, just 221 heat pumps have installed in homes in Brighton and Hove since 2009 – covering an estimated 0.2 per cent of households.
To help boost the number of pumps installed, the government has just announced it will increase the grant from £5,000 to £7,500. It also pledged to fit 600,000 pumps by 2028.
In the past year, 57 homes in the city have been fitted with a heat pump, though officials still say more needs to be done.
But despite the calls for action, PM Rishi Sunak promised last week to roll back demands on landlords to improve the energy efficiency of their properties and upgrade old boilers.
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 said: "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."