The King’s two Bentleys are due to be converted to run on biofuel within the next 12 months as part of a wider sustainability initiative.
In the long term, the plan is to switch to official electric vehicles.
The royal household’s annual accounts published on Wednesday revealed a series of new, more environmentally friendly measures.
Taxpayer funding for the running of the Royal Household will be £86.3 million in 2023-24, the same as the previous year.
This funding, which covers things like official visits and residency, is known as the “sovereign grant.”
Prince Charles has been campaigning on climate issues for decades, but the latest accounts for the first financial year of the monarch’s reign show he is determined to change his tack.
Windsor Castle will be fitted with solar panels for the first time, while Buckingham Palace’s gas lights will be replaced with specially designed appliances to improve energy efficiency while preserving its historic look and sparkle.
Cabinet Secretary Sir Michael Stevens said the green initiative was “borne out of our determination to put sustainability at the heart of our business and inspired by Her Majesty’s leadership in this area”.
Prince Charles has previously said that people thought he was “completely crazy” when he started speaking out about the environment in the 1970s.
The annual accounts were delayed by a month due to the general election.
The royal family has revealed that they will receive two new helicopters over the next 12 months to replace their existing 15-year-old helicopters.
The report said helicopters were a “critical element” in enabling the monarch and members of the royal family to carry out official duties and access remote parts of the UK.
There are also efforts to increase the use of sustainable aviation fuel for Royal flights, where feasible.
Overall, natural gas and heating emissions across the Royal Estate fell by 3%, but total greenhouse gas emissions were slightly up from the previous year, the report said.
This is mainly due to increased emissions from business travel compared to 2022-2023, when royal travel was restricted due to events surrounding the change in royal rule.
A 10-year, £369 million project to restore Buckingham Palace is underway.
A separate report by the National Audit Office (NAO), published on Tuesday, concluded that the refurbishment was generally well managed, but warned that the discovery of asbestos, which led to structural damage and increased costs, “could have been foreseeable”.
The company announced that 82% of its operational improvements are complete.
According to the NAO, work completed included installing a new boiler, switchboard and backup generator, relocating water tanks and removing dangerous electrical cables.
Frogmore Cottage, the former home of the Duke and Duchess of Sussex, remains empty, more than a year after the couple officially left.
Speaking at a briefing on the royal family’s finances, palace officials said the Grade II-listed royal property at Windsor Home Park would not have any new tenants.
“A rapidly changing situation”
The period covered by the financial report will run from 1 April 2023 to 31 March 2024, covering the coronation and coronation celebration moments of the King and Queen.
But it has also been a more difficult time for the family after both the king and queen were diagnosed with cancer earlier this year.
Sir Michael acknowledged this, saying some of the events mentioned “may seem ancient given what has happened since then”.
“We are saddened to announce that His Majesty The King and The Princess of Wales will be temporarily stepping back from royal duties at the start of 2024 to prioritise his cancer treatment and recovery.
“This has inevitably had an impact on the number and nature of planned engagements. However, I wish to say it is very encouraging to see The King back on track with many engagements, and that The Princess has recently felt well enough to take part in the King’s Birthday Parade and the men’s Wimbledon final.”
Overall, there were more than 2,300 official events for Members of the Royal Family both in the UK and abroad, up from more than 2,700 last year.
Prince Charles performed 464 engagements despite being diagnosed with cancer.
The most expensive was an official visit to Kenya, which cost £167,000.
“Behind the scenes, the work of the Royal Family continued smoothly during the second half of the financial year, with His Majesty continuing to fulfil all his duties of State, Her Majesty The Queen undertaking many of her official duties and support teams adapting quickly to the changing circumstances,” Sir Michael added.