Scottish Government plans to overhaul how homes are heated risk jobs and soaring energy bills, a leading trade union has warned – amid calls for the strategy to be “properly planned, tested and costed”.

The Herald on Sunday exclusively revealed Patrick Harvie’s proposals to modernise energy performance certificates, with traditional fossil fuel gas boilers set to be penalised in a bid to encourage people to clean up heating systems.

The Scottish Government draft plans will “encourage” people to take up heat pumps as part of plans for all homes to meet certain energy efficiency standards by 2033 and one million homes to be decarbonised by 2030.

Read more: Gas boilers set to be penalised under energy efficiency overhaul

But the GMB Scotland union, the biggest trade union in the energy sector, has raised fears with the strategy – claiming it could lead to increased energy bills and put jobs at risk.

Mr Harvie has stressed that the strategy “has the potential to cut costs for all of us in the long run”.

Union leader have written to Mr Harvie, the Greens Zero Carbon Buildings Minister, asking for urgent talks and claiming his plans to ban gas central heating are rushed and unrealistic.

The GMB has accused the Scottish Government of needlessly risking jobs in the North Sea oil and gas sector, off and on-shore, undermining Scotland’s energy security and risking huge bills for households being encouraged to install new technology untested in Scottish homes.

Read more: Patrick Harvie criticised for ruling out hydrogen boilers

Claire Greer, GMB Scotland organiser in energy, claimed the cost of installing heat pumps, for example, will be prohibitive for most households and, even with grants, will force many into debt.

She has also claimed that if energy companies are expected to foot the bill, the costs will be passed on ton consumers in higher bills.

The union has also claimed that the cost of new homes could also increase if gas heating is banned, as suggested, next year.

Ms Greer said ministers must assess the drive towards new, greener technology to ensure the costs can be detailed, the technology tested and the impact on jobs and energy security assessed.

She said: “Heat pumps and other new technology will run on electricity which is more expensive than gas and, so far, ministers cannot explain how energy needs will be met by electricity alone.

“The economic, social and strategic importance of gas cannot be understated and demands policy-making that is properly planned, tested and costed.”

Instead of spending billions of pounds removing gas networks, Ms Greer has called for ministers to increase investment in new hydrogen technologies provided through the existing network, adapted using the expertise of gas engineers.

Read more: Two thirds of Scottish Government buildings fail energy targets

She said: “The road to net zero simply cannot be paved with the livelihoods of tens of thousands of gas workers when a viable alternative exists.

“We hear a lot about the supposed ‘just transition’ but there is nothing just about the impact on workers in the energy sector and there is nothing just about households forced to endure unnecessary costs and higher bills.”

Around one fifth of Scotland’s carbon emissions come from heating buildings.

A Home Energy Scotland initiative allows grants of up to £7,500 to install both heat and energy efficiency measures, with additional funding available for some rural properties.

The Scottish Government said it remains committed to developing the hydrogen economy, but has ruled out hydrogen-ready boilers which produce carbon emissions being used as a suitable placement for traditional fossil fuel heating systems.

Read more: Half of Scots support Harvie's plan to phase out fossil fuel boilers

Mr Harvie has insisted that switching homes to low-carbon heating systems is “essential” if Scotland is to meet its legal climate targets, adding that the strategy “has the potential to cut costs for all of us in the long run, and make us less dependent on volatile and increasingly expensive fossil fuels”.

He added: “Polling suggests that the majority of people in Scotland want to see that change happen.

“Heat pumps are a proven heating technology which have been around for decades and are used in countries across Europe. Of all of the UK nations, Scotland has the most generous grants available to households that want to switch to climate-friendly heating systems.

"We estimate that 16,400 jobs will be supported across the economy in 2030 as a result of investment in the deployment of zero emissions heat, with further jobs supported through retrofit energy efficiency works.

“We published our Heat In Buildings Strategy almost two years ago and, later this summer we will consult on proposals that might be included in a Heat in Buildings Bill and aim to set out further details of any planned new regulations.

"We want to hear from as many people as possible, across all areas of Scotland, on ways to help us ensure that we design the right protections and exemptions from the start – making sure the transition is just, fair and effective.”