This article appears as part of the Unspun: Scottish Politics newsletter.

The empty rows where SNP backbenchers normally take their seats in Holyrood during ministerial statements said it all – anxiety and scepticism.

Only a few of the party's MSPs were present as the government's zero carbon buildings minister and Scottish Greens' co-leader Patrick Harvie unveiled his heat-in-building plans on Tuesday. None of those who spoke seem particularly ready to give the proposals a glowing endorsement.

Unspun has heard that just an hour or so earlier, at the weekly group meeting for SNP MSPs over lunchtime, the topic of heat pumps was the main matter exercising the minds of SNP MSPs.

Cabinet secretary for net zero Mairi McAllan was pressed repeatedly about the policy by concerned members seeking reassurance which some say she was unable to give.

"People were raising serious concerns. There was a different mood from usual. People asking questions weren't looked upon askance by the loyalists," said one source.

"Perhaps for the first time there is a realisation these policies are doing us no good at all. Some backbenchers are getting worried about their own seats and that worry is starting to concentrate minds."

Another source said starkly of Mr Harvie's plan: "Voters are not going to like it."

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Insiders said there was some relief among SNP MSPs when Mr Harvie announced that the government would be axing the target to have the heating systems of more than one million homes run by heat pumps or other green energy sources by 2030.

Confirmation of a report in The Herald on Sunday that off grid homes would not have to start phasing out fossil fuels boilers in 2025, as originally mooted, was also welcomed.

The proposals that remain in place include a target to have all homes in Scotland run by green sources of energy by 2045 (the date by which the country should reach net zero); new energy efficiency standards, which could take the type of heating system into account, as well as insulation and fabric of the building, to be met within the decade.

The Herald: A report in The Herald on Sunday that off grid homes would not have to start phasing out fossil fuels boilers in 2025 was confirmed by the plansA report in The Herald on Sunday that off grid homes would not have to start phasing out fossil fuels boilers in 2025 was confirmed by the plans (Image: Newsquest)
Private landlords will need to meet the requirement by 2028, while owner- occupied homes will need to meet those same standards by the end of 2033.

But with estimates – made in 2021 – that the policy will cost some £33 billion and that to date just £1.8billion has been set aside from the public purse to help fund it – concerns remain that almost all of the financial burden will fall on individual households.

There are fears that one of the SNP's key messages at the general election – a promise to deliver on the cost of living crisis – is being seriously undermined – and that heat pumps could leave the party vulnerable to attacks from the Conservatives and Labour.

Backbenchers – some of whom gathered at a party meeting at Stirling University on Saturday to discuss the general election strategy – feel they have a popular policy with the council tax freeze (saving households hundreds of pounds) to take round the doors on the campaign trail in the coming months.

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They are less convinced of a positive reception to the government's suggestion that households take out loans or extend their mortgages by up to tens of thousands of pounds to retrofit their homes with insulation, heat pumps and double glazing to comply with new energy efficiency standards when many households are struggling to meet their existing monthly payments.

There is anger about possible plans to penalise people whose homes don't comply. In Holyrood on Tuesday Mr Harvie did note there would be no such penalties in the "foreseeable future".

“We have looked at the option of civil penalties in relation to landlords who fail their tenants by not investing in bringing properties up to standard. We have not suggested that there would be, at least in the foreseeable future, a role for civil penalties in relation to home-owners," he said.

Speak to SNP backbenchers and they are concerned the whole debate is going to get worse for the government rather than better as industry bodies start responding to the consultation.

Criticisms are likely to be made from a whole host of bodies – estate agents, surveyors, gas boiler manufacturers and organisations representing heating engineers – all of which are bound to generate a new set of negative headlines.

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All this appears to be leading up to an SNP pushback with some in the party hopeful that the plans will be further watered down by ministers when they are confronted by alarmed households and businesses.

They point to previous ministerial decisions to drop the highly protected marine areas plans and the deposit return scheme as precedents for the way the government may act.

"They've already had to make some concessions [on heat pumps] and there is a sense the mood will harden against these plans," said a source.

It's a policy which has a long way to go but around Holyrood there's a sense that if SNP MSPs get their way behind the scenes in the coming months there may be no need for a rebellion when considerably watered down heat-in-building proposals are finally voted on in the Scottish Parliament.