Answering the big questions on removing gas central heating from Scotland's homes

The figure was a measure of what proportion of Scottish heat comes from oil and gas. It was 93.3%.

Scotland has one of Europe’s best records on clean power. And one of its worst on clean heat.

With ambitious targets to get to net zero carbon by 2045 for Scotland and 2050 for the UK, householders and housebuilders, tenants and landlords, have got remarkably little time to wean themselves off now traditional gas boilers.

The Scottish Government this week made its first and - observers say - easiest steps. Starting in 2024, all new-build homes will have to have carbon-neutral heating. That is not as tough as it sounds.

An entire neighbourhood with district heating built using heat pumps made by a Scottish firm has just opened in Clydebank.

There are other renewables sources of heat too. The oil and gas industry favours hydrogen. There is biomass. And even in the chilly north of Britain, solar energy has a role to play.

But most scientists, including those who advise the Scottish and British governments, think heat pumps will do the heavy lifting of heating our homes, and providing hot water for our baths, showers and dishes.

So far nobody is suggesting that old gas boilers - and remaining oil ones in rural areas - be stripped out all at once. The idea is to gradually replace old technology with new. True, the Climate Change Committee or CCC, the body which helps guide UK and devolved governments on tackling global heating, this week called for gas boilers to be banned by 2033 under its “blueprint for a fully decarbonised UK”.

With the start-up costs of a heat pump system in a private home three times higher than a fossil-fuel boiler, that got some householders due to replace their central heating a little worried. Subsidies are available to make the change, to help with up-front costs.

Decarbonising the UK economy does not come cheap; though the CCC estimate for costs has fallen to under one per cent of GDP a year. Heating is going to be a big part of the transition cost. So what is happening with green heating? We asked some experts.

Why are we switching away from gas and oil boilers?

This is the easy question. “It is climate change,” says Fabrice Leveque, head of policy at WWF Scotland. “Gas boilers typically emit several tonnes of greenhouse gases into the atmosphere each year, and are one of the largest single items on a person’s own carbon footprint.”

Scotland’s huge estate of central heating systems accounts for half the country’s energy use and more than half of its carbon emissions.

It also makes our air dirty, Back in the 1970s gas heating revolutionised Scotland - replacing filthy coal. The air felt cleaner. Getting rid of gas will make another difference.

Scottish Renewables, the industry lobby, whispers another reason why governments are moving away from gas: energy security. North Sea gas will not last forever.

What are the alternatives to oil and gas?

That depends where you live - and in what kind of house. “Some old, hard to insulate rural homes might need to use wood-fired boilers,” explained Leveque.

But the growing consensus is that heat pumps - whether for district heating networks or -individual homes are going to be the biggest alternative.

This technology is not new. The Belfast-born but Glasgow-based scientist William Thomson - better known as Lord Kelvin - came up with the idea smack in the middle of the 19th century, the steam age.

Heat pumps which works like a fridge or air conditioner in reverse to generate warmth from the difference in two temperatures. They need electricity and a source of heat - usually the ground, the air, or, as is the case with the recent Clydebank development, water; the River Clyde.

Matthew Black works for Kensa, a Cornish firm which makes and installs ground-sourced heat pumps. He explained how the system works. “Once the heat has been gathered, for example from the ground, the heat pump in your home then uses the vapour compression cycle (invented by Lord Kelvin) within the appliance to upgrade the heat from a lower temperature to a higher temperature and delivers this within your home for use.

“Importantly, two thirds of the heat has come from the local environment, in this example the ground, and only one third has been generated by the compressor within the heat pump using low carbon electricity to do so.”

How much will this cost?

As with electric cars, there may be some higher upfront costs with occupiers - hopefully - saving in the long run on their bills as better insulation and lower running costs.

A heat pump costs from £6000 and up to buy and install - and the price can get even bigger for people replacing radiators at the same time.

“The installation cost of heat pumps is more expensive than the current mains gas heating systems most of us are used to.” Mr Black of Kensa acknowledged. “This is unlikely to change anytime soon.”

“However, when we consider the long life of the equipment and infrastructure, the future increase in gas prices and the negative impact gas has on global climate change and public health the heat pump wins hands down.”

However, Helen Malone, senior policy manager at Scottish Renewables, reckons more incentives are needed to help encourage alternative heat on top of cash-back grants and loans already available from Home Energy Scotland, and the UK Government’s Renewable Heat Incentive.

She said: “As more and more of those alternative technologies are installed, their cost will fall.

“Fluctuations in the price of imported gas, in particular, have made life difficult for UK energy consumers in recent years, with around a quarter of Scottish homes in fuel poverty.

“Renewable electricity is now the cheapest form of energy generation in the world, so using this home-grown fuel instead of imported gas will increase the security of our energy supply as well as cutting costs.”

The question for consumers - especially those with gas boilers coming to the end of their lives - is when the price point will change to make a heat pump the clear favourite. Around 100,000 new boilers are installed in Scotland every year, replacing old ones. Right now most are gas.

Do we really need individual heating systems?

This is the game changing question. Most northern nations have some form of shared heating: whether it is a North American-style single boiler room for a multiple occupancy building or the kind of gold-standard district heating enjoyed in Scandinavia or the former Soviet Union.

Malone points out that 97% of homes in Copenhagen are heated on a district network of hot water pipes. This has potential in Scotland, she said.

“A recent Scottish Renewables study highlighted an ambitious programme of new networks that could serve up to 8% of Scotland’s heat requirement by 2030 and would require a multi-billion pound investment,” she said/ Around 40% of that spend would be on civil engineering, creating opportunities for local construction supply chains across Scotland’s cities.”

But multi-home heating does not necessarily mean digging up roads and installing massive infrastructure. “Smaller heat pump systems can also be shared between neighbours, reducing costs for everyone,” said Leveque.

One of the most obvious potential customers for district heating systems are social landlords - not least because their tenants are among the most likely to be in fuel poverty.

Will there be enough hot water for my whole family?

Burning fossil fuels heats up water fast. Some consumers fear a heat pump, at least an individual one, will be slower. Black of Kensa says that should not be the case if a system is properly installed.

District heating is an even better bet. Such systems, said Leveque, have a “huge capacity to provide hot water, as they are designed to serve entire neighbourhoods rather than the small systems we currently have in our homes”.

What will happen to gas fitters?

Scotland has an army of central heating specialists busy installing and maintaining boilers, pipes and radiators.

Many of the skills are transferrable to the new world of heat pumps and other alternatives.

“Heat pumps, like the gas boilers they’ll replace, need an annual check-up, where anti-freeze levels are tested, flow rates analysed and controller settings are optimised,” said Malone. “Lessons from continental Europe, which is far ahead of us in decarbonising heat, show homes which switch away from gas will need advanced insulation, too.

“Here lies more opportunity: a chance for today’s heating engineers to become all-round energy advisors, working with homeowners to optimise their lives, installing smart equipment and controls and remotely monitoring their performance to make the most of the energy which is being used.”

Will Scotland have enough electricity to keep heat pumps working?

Heat pumps will only work if we can plug them in. That means Scotland will need a investment in technology to generate, transmit and store renewable energy. Energy companies say they can deliver. Keith Anderson, chief executive of ScottishPower, said: “We’re about to invest £10bn in the next five years, doubling our renewable energy generation, once we’ve done that, we’re going to double it again. We’re also investing in the network to take this green generation to power homes and businesses across the country.”