The Scottish Government has missed a target for 11% of non-electrical heat to be generated by renewables in 2020, with the figure falling slightly from 2019.
A report found the total non-electrical heat coming from renewable sources such as biomass or heat pumps was at 6.4% in 2020, down from 6.6% in 2019.
The decline was put down to a reduction in output by several large biomass facilities, however the economic impact of the pandemic may also have reduced demand.
The Scottish Government said there had been a steady increase in the number of heat pumps being installed every year, with 3,020 new installations reported in 2020.
Under the latest strategy to decarbonise Scotland’s buildings, which is being overseen by Green minister Patrick Harvie, one million homes and 50,000 other premises will need to transition to low-carbon heat by 2030.
The 11% target for renewable heat was set as part of the Climate Change (Scotland) Act in 2009.
The Energy Saving Trust produced a report on progress towards the target for the Scottish Government.
It said: “The decrease in renewable heat output and progress towards the renewable heat target between 2019 and 2020 is largely due to changes in operation at a small number of very large biomass sites.
“Their reduction in output masked the growth in output from new biomass installations and those of other renewable technologies.”
The Government’s own progress report said: “Whilst biomass and biomethane dominate renewable heat generation, there has been a steady growth in heat produced by heat pumps.
“Heat pumps saw the largest increase in number of installations and output with an additional 3,020 installations contributing to an additional 83GWh of output, compared with 2019.
“This brings the total heat output from heat pumps in Scotland to 390GWh and the total number of installations to around 21,000.”
Increased energy efficiency has also reduced demand for heating, the Government said.
Scottish Labour MSP Monica Lennon said the SNP has failed to match rhetoric on the environment with action.
She said: “Despite all their warm words, the SNP’s track record on the environment is one of failure.
“Not only have they missed yet another key target, but things are actually getting worse.
“With Cop26 a matter of days away, this exposes the gulf between SNP rhetoric and reality.
“Being a world-leader on the environment requires deeds not words – the First Minister should take her own advice and deliver credible action.”
Holly O’Donnell, climate and energy manager at WWF Scotland, said the missed target is “disappointing”.
She said: “The pandemic will have disrupted progress in 2020 but even before this, the rollout of energy efficiency, heat pumps and heat networks was too slow.
“The recent rise in gas prices is an urgent reminder that the move to renewables isn’t just good for the climate, it can protect us against volatile fuel prices and create new green jobs.
“We need to see stronger regulation and incentives from the Scottish Government if it’s to meet its target of switching a million homes to renewable heating by 2030.”
A Scottish Government spokesman said: “Deployment of renewable heat has seen challenges over the past decade, including uncertainties caused by the UK Government’s approach to changes to the Renewable Heat Incentive scheme over its lifetime.”
He continued: “We know that we have to go further and faster, but we are being held back by glacial progress in the UK Government.
“While their new Heat and Buildings Strategy includes some measures which will complement the comprehensive support package already available in Scotland, the overall plan for action and investment levels fall well short.
“We will continue to work with the UK Government as it implements its strategy and call on it to accelerate action to support and enable delivery in Scotland, such as reforming the energy markets and amending the Gas Act.”