More than 100,000 homes could avoid the need to install heat pumps over the next two decades as part of an ambitious blueprint to ramp up district heat networks across Scotland.

Proposals to clean up how buildings are heated could mean one-third of Scotland’s heat demand comes from heat networks – with potentially as many as 140,000 homes, largely in towns and cities, avoiding the need to install individual heat pumps.

But Scotland is set for a long-term shift to renewable heat technology and is already lagging behind many European countries, with heat networks to be combined with ramping up heat pump installations and other individual solutions as part of one of the most difficult and costly government strategies being rolled out.

The Scottish Government’s Zero Carbon Buildings Minister, Patrick Harvie, has launched a key consultation on his strategy for requiring changes to be made to how buildings are heated.

Under the draft plans, all buildings must stop using fossil fuel gas boilers by 2045 and switch to renewable heating systems.

The plans set out that by 2028, private rented homes will need to meet new and modernised EPC C standards which will take the heating system such as a boiler or a heat pump into account, while the same rules will apply for all domestic homes by 2033 – ahead of all buildings being on zero direct emissions heating systems by 2045.

By April next year, newly-built properties will be banned from installing gas boilers.

Households installing heat pumps will play a key role in the strategy, with the device suitable for large numbers of properties.

But heat networks, which are essentially a network of pipes run off a large heat pump or other source powering a series of buildings, could be used for almost one third of Scottish homes by the end of the decade.

Heat networks or district heating systems use heat from a variety of sources such as waste heat from large buildings like hospitals and shopping centres, or from industries such as distilleries.

The technology can even extract heat from waste water treatment plants - like a network in Stirling which uses heat from sewage treatment to heat a local leisure centre, a school and will ultimately be extended to heat homes in the area.

Heat networks can also be connected to large heat pumps which can extract heat from the air, rivers, or the ground.

Already, more homes in Scotland are connected to heat networks than have individual heat pumps installed – and that potential for heat networks is due to soar in the coming decades – particularly for large new housing developments.

There are currently more than 1,000 heat networks in Scotland, supplying around 1TWh of supply.

As things stand, roughly 28,000 homes and 2,4000 non-domestic buildings are connected to heat networks in Scotland.

Most of Scotland’s current heat networks are relatively small in scale but some newer projects are being brought forward at a larger scale.

But the Scottish Government has set a target for 2035 of 7TWh from heat networks – which would likely result in a five-fold increase in the number of homes connected, which would be roughly 140,000 properties.

However, the number may be lower due to a higher proportion of non-domestic buildings being useful as anchor points for the heat networks.

Research has revealed that heat networks have the potential to cover between 18% and 32% of Scotland’s heat supply as they ramp up in the next decade.

Mr Harvie said: “Across Europe, almost every country is changing the way we heat homes and other buildings, moving from fossil fuel heating to clean heating.

“And that means a mix of communal and individual systems.

“It’s not either/or. It’s both. Scotland is no exception: different types of buildings in different areas need different solutions, and heat networks will have a major role to play in helping us to make that transition.”

He added: “We believe we can meet up to 30% of our heat demand from heat networks, which is why our heat in buildings consultation includes measures to encourage their growth, giving developers and local authorities the confidence to invest on the basis that they know the demand will be there.”

SNP and Green ministers are hoping to encourage the rapid expansion of heat networks over the next decade – including funding and technical support to councils to draw up local heat and energy efficiency strategies which will identify where heat networks could be developed across the country.

The Scottish Government is hoping to encourage businesses to set up heat networks or be district heating anchor points with 90% rates relief until March 2024 for new networks run from renewable sources – while all heat networks have 50% rates relief until 2032.

As well as the Scottish Government’s long-standing district heating loan fund, £300 million has been made available to develop and roll out heat networks across Scotland.

Public sector organisations are now required by law to complete building assessment reports that investigate which public buildings could be connected to heat networks.

Ministers could go further and are exploring potentially legislating to encourage certain buildings to connect to heat networks.

The Scottish Government legislation could provide powers to local authorities or to ministers that “require developers to connect new buildings within heat network zones to a heat network”.

The proposed heat in buildings legislation, if approved, would make legal requirements for fossil fuel heating systems being ripped out at certain points – which government officials hope will strengthen the business case and encourage the ramping up of heat networks.

The plans also propose heat networks ending their use of non-renewable sources “by a certain date and with a minimum notice period”.

But those connected to heat networks will be exempt from having to make upgrades to energy efficiency standards when properties are sold in a bid not to spook investment in the technology.

Under the proposals, buildings within a heat network zone “will not need to meet the heat in buildings standard following a property purchase”.

It adds: “This is to preserve the business case for a new heat network development by ensuring that buildings which are likely to connect are not forced to adopt another system before time.

“These homes and non-domestic buildings will be required instead to meet the heat in buildings standard when a heat network becomes available – either by connecting to the network or by choosing to install another clean heating system.”

But campaigners, who have welcomed the strategy, has called for the Scottish Government to put up more funding to help scale up heat networks.

Fabrice Leveque, climate and energy policy manager at WWF Scotland, said: “Low carbon heat networks will be critical for cleaning up heating in urban areas.

“They can distribute heat drawn from sources like parks, rivers and old mines, and provide an alternative for homes like flats, which might not have space for an individual heat pump.

“Local authorities are identifying areas where heat networks are likely to be the best option, and a vital next step will be developing plans to get these networks built quickly.

“Greater financial support from the Scottish Government is crucial to carry out this work at the scale needed to meet our climate targets.”