As many as 14,000 Scottish homes still use coal as their main form of heating, a report suggests.
The figures, provided by industry body Scottish Renewables, indicate homes using coal must switch to cleaner alternatives if Scotland is to hit its climate change targets.
A home heated by coal emits up to five times more carbon than one heated using a modern heat pump.
The Scottish Government has set a target that 35% of residential heat should come from renewable sources by 2030.
The UK Government funds households switching to low-carbon heat through the Renewable Heat Incentive, with owners eligible for payments for every unit of low-carbon heat they produce.
The scheme is currently funded until April 2021, while the Scottish Government also provides interest-free loans to help consumers switch.
Fabrice Leveque, senior policy manager at Scottish Renewables, said: “Coal-powered electricity generation has already become a thing of the past in Scotland and it is time household coal heating was consigned to the dustbin of history, too.
“Schemes like the Renewable Heat Incentive are available to help people switch to more sustainable alternatives and the benefits of doing so are clear – cleaner air, a healthier environment and less of the harmful emissions which cause climate change.
“The Scottish Government’s Energy Efficient Scotland programme launches in 2020 and we would like to see it tackle the issue of coal heating, as well as the polluting oil and LPG systems, which remain so common in the large areas of Scotland which do not have a mains gas supply.”
Gina Hanrahan, head of policy at WWF Scotland, said: “It’s really saddening to learn so many homes in Scotland are still forced to rely on dirty coal as the main source of heating.
“We know ending our use of fossil fuels is not only good for the environment but also for our health.
“Heating our homes and buildings accounts for around half of all our energy and climate emissions.
“It’s time we saw bold leadership and action from the Scottish Government to accelerate the decarbonisation of our homes, especially in off-gas grid areas.”