Domestic solar panels can save between £974 and £1,151 a year on average on energy bills. Image: Green MPs (flickr).

Caroline Lucas has called on the UK government to make solar panels mandatory on the roofs of all suitable new homes.

Speaking yesterday (Wednesday 22 March) in a Westminster Hall debate on solar rooftop installations, the Green Party MP laid out the potential solar could offer economically and environmentally if the installation of the technology was further supported by a government mandate.

Lucas applauded the government’s target of 50GW of solar by 2030 and then 70GW by 2035, up from of 15GW today. Of the current capacity, around two thirds is made up of ground-mount installations, with the remainder residential and commercial rooftop installations according to Solar Energy UK.

“This morning, I want to make the case for the installation of solar panels on all suitable new-build homes to be made mandatory and to explore how to overcome some of the obstacles to domestic solar,” she said as she opened the debate.

‘A win-win policy’: Reducing energy bills

Jim Shannon, the MP for Strangford in Northern Ireland, endorsed Lucas' request, highlighting that solar can both increase the value of a property and help reduce the energy costs of those living in the property.

“This is a win-win policy: it is good for householders and good for the environment, and it is good to get people’s bills down too. I thank him for that intervention, with which I entirely agree,” responded Lucas.

“Some 80% of the buildings that we will have in 2050 have already been built, and we must work hard to retrofit them with renewables, but the remaining 20% have still to be built, and maximising the deployment of on-site solar generation in new-build homes could be a real game changer. If we are serious about continuing and accelerating what has been achieved to date and generating a successful rooftop revolution, we should be mandating that all suitable new homes come with solar panels as standard. The government have an opportunity to do that with the new future homes standard.”

She continued to highlight the popularity of solar, which would support the introduction of mandated installation, point to a recent YouGov poll that found that 80% of people across the UK would support the government bringing in regulations to ensure solar panel are a default on new houses. Meanwhile, just 9% voted against the idea.

John Stevenson, the MP for Carlisle in Scotland, also expressed his support for Lucas’ proposal during yesterday’s session.

“It feels a bit like groundhog day, because in September 2017 I had a Westminster Hall debate on this very subject. Had the government followed her suggestion, we would have 1 million new homes with solar panels today. Does she agree that making this compulsory would not only lead to 150,000-plus houses per year getting solar panels but would, in time, lead to price reduction, making it cheaper, and innovation?” asked Stevenson.

Lucas agreed with him, stating that the current estimates suggest that households can save between £974 and £1,151 a year on average on energy bills.

Additionally, further research from Solar Energy UK found that installing a residential solar system on a new build property is 10% cheaper than retrofitting it on an existing property.

There will be properties where it is not suitable to install, Lucas said in response to a recent petition on the issue that attracted 15,000 signatures, but there is still value in mandating the installation of panels.

‘Many different ways to skin a cat’: does a mandate mean a loss of options?  

She moved on to rebuff statements made by the Secretary of State for Energy Security and Net Zero during an Environmental Audit Committee hearing last week.

Grant Shapps MP said: “We know that there are many different ways to skin a cat; decarbonisation, heat pumps, whether ground-source or air, could be a solution. If you start to say this is the only technology you can use and the only solution you use, you are in danger of losing out on a potentially better solution in that particular location.”

However, Lucas noted that insisting on solar panels is far from saying that they are the only renewables allowed. She highlighted that actually the combination of solar with heat pumps was often cheaper to run as well as being good for the environment.

A second point raised by Shapps was the suggestion that the installation of solar on new homes would increase the cost of properties. The government’s changes to part L of the Future Homes Standards however already includes the need for further energy-saving and low-carbon heating technologies, which will have costs attached.

“The average price for solar panels is around £5,000; if someone wants batteries on top, the cost is between £1,200 and £6,000, according to the Energy Saving Trust,” said Lucas.

“However, that is a relatively small fraction of the cost of a new home and it would quickly be more than offset by the many benefits and cost savings across the economy, including lower bills for the householder, as the hon. Member for Strangford has indicated. There is evidence that solar panels add value to a house – an average of £1,800. In addition, there are ways for the government to mitigate any increases for house buyers, which I will say a little bit more about shortly.”

Research from RewewableUK found that mandatory solar panels and heat pumps in new home would add around £8,000 to the cost of a new home, a figure that would decrease as installations gather speed. This is no more than a 4% increase on the average new house prices of £180,000. This could also be reduced if the government were to offer interest-free loans for the technology.

Shapps suggested that the global supply chain challenges for things such as critical minerals would cause an additional housing crisis if solar panels were mandated. But with the right political will it is perfectly possible to source materials outside of China where the bulk of the current problems lie, Lucas counters.

Additionally, there are alternatives to silicon such as perovskites, which could be sourced and supplied outside of conflict regions. Perovskites are still nascent in comparison to polysilicon based solar panels however, although recent breakthroughs include the Australian National University achieving a 30.3% efficiency rate for a test-size perovskite-silicon tandem solar cell, suggesting that they could soon play a larger role in the sector.

The final criticism of mandatory solar panel installation from Shapps was that it would stifle innovation. Lucas pushed back against this suggesting that expanding the market through mandatory installation rather than relying on the smart export guarantee, as the government has done heavily in the past, will actually encourage further innovation.

“With the UK seeking to build 300,000 homes a year by the mid-2020s, the industry would have a steady market, creating the conditions for innovation, greater efficiency and therefore lower costs. That would be in marked contrast to the stop-start approach that the right hon. Member for Kingswood (Chris Skidmore MP) identified in his net zero review as a significant barrier to the investment needed to meet our renewables target,” said the Green MP.

Providing predictability to spur growth

One of the key benefits of mandating the installation of rooftop solar on all suitable new build homes, instead of simply presuming that future homes will come with renewables 'baked in', is predictability.

“From successive governments since 2010 we have had the zero-carbon homes standard, the code for sustainable homes, feed-in tariffs, smart export tariffs, the energy company obligation and green homes grant. It is no wonder the net zero review found that lack of confidence in “inconsistent” government is a huge barrier to renewables investment. That needs to change. As we know, house builders will build to the regulations,” said Lucas.

Rooftop solar in Britain can already be viewed as a success story, despite the ups and downs of the ‘solarcoaster’ driven by the stop-start policy framework.

Last year there were more than 130,000 rooftop solar arrays installed in the UK, more than double the figure in 2021. Installers up and down the country have been reporting record levels of interest, with many struggling to keep up with demand and working to expand their operations at pace.

But to hit targets, this pace of installation will have to double again, with an average of 4.3GW per year of solar needed, up from 3.2GW installed in 2022.

This is “clearly achievable” though, noted Lucas, and is in fact lower than what was installed in 2011 and 2012 during the height of the feed-in-tariff era.

Breaching the skills shortage

There will be a few key obstacles to tackle if the pace and scale of installations are to be increased to meet the needs of a solar installation mandate for new build properties. Most noticeably, the restricted availability of equipment and an acute skills shortage.

Lucas highlighted that irregardless of a mandate, the solar supply change will have to develop, expand and diversify, in particular increasing its transparency standards. If anything, the requirement for solar caused by a mandate would spur this process on.

“Overcoming the skills shortage is equally important. It demands a skills and training revolution – a solar army,” she continued.

“The industry estimates that the 70GW target could take us to 60,000 jobs in the UK. The previous peak was in 2014, when solar had 20,000 employees. But those new jobs need people to fill them. At present, from manufacturing to construction and engineering, from maintenance to data analysis, there is a growing gap between what is required to deliver on solar and the skills base that is coming through our training and education pathways. Solar builders are also competing against the wind and automotive industries for workers.”

The mandate could drive demand, which then could help clear bottlenecks with regards to retraining workers. Around 70% of oil and gas jobs have a skills overlap with low-carbon roles, and already around Europe we’re seeing the potential of retraining these masses seized, according to Lucas.

“When I asked the minister about solar at the last Department for Energy Security and Net Zero oral questions, he said he wanted to 'go further and faster',” finished Lucas.

“During last week’s Budget statement, the Chancellor proudly proclaimed that he was fixing the roof while the sun was shining. Both of those signs are encouraging, so I hope the government will back solar in an even bigger way, starting by making it mandatory on all suitable new homes. It is a win-win policy, lowering bills and those all-important carbon emissions, while massively boosting our thriving renewables sector, improving energy security, creating hundreds of thousands of good-quality jobs and helping to level up, all at no cost to the taxpayer. That is what a rooftop revolution looks like, and that is how to ensure targets get delivered.”


Solar Power Portal's publisher Solar Media will host the UK Solar Summit on 27-28 June 2023 in London. The event will explore UK’s new landscape for utility and rooftop solar, looking at the opportunities within a GW+ annual market, and much more. For more information, go to the website.