Charles installed solar panels on part of the Windsor Castle estate known as the Lord Chamberlain's Upper Store, replacing the existing lead roof, and the plan will be to add more panels in the future, officials said.
The Royal Family has Bentley limousine cars and these will be converted to run on biofuel in the next year as an interim step before the household's fleet of cars eventually becomes electric, the officials said.
Charles has long been outspoken on conservation and in 2020 described global warming and climate change as the greatest threat that humanity has faced.
Palace officials provided the information as they explained details of the annual report into the King's taxpayer-funded spending and income, known as the Sovereign Grant, published on Wednesday.
This showed that official expenditure for 2023-24 had been £89.1 million (NZ$150 million), above the £86.3 million allocated, forcing the royal household to dip into reserves to fund the deficit, though by less than last year.
Overall expenditure fell by 17% compared with the financial year 2022-2023, helped by a £10.8 million fall in the cost of property maintenance.
Additional income to supplement the Sovereign Grant more than doubled to £19.8 million helped by a rebound in ticket sales to visit royal palaces, which almost returned to the levels before the Covid-19 pandemic.
The Crown Estate, which comprises tracts of land and most of Britain’s sea bed, is an independently run, commercial business, whose profits go to the Treasury. They are also used as the benchmark for the level of public funding for the Royal Family.
The royal family also plan to take delivery of two new helicopters this financial year, the accounts show. The report justified the cost of the new helicopters, saying the existing ones are 15 years old, and it will help members of the royal family complete multiple engagements on a single day.
Overall, travel costs amounted to £4.2 million, with the biggest overseas expense Charles and Queen Camilla's state visit to Kenya which cost £167,000.
Meanwhile, the Crown Estate, which manages the King's public property, posted a record profit for 2023/24 of £1.1 billion, boosted by income from offshore wind leases, its results showed.
The Crown Estate, which comprises tracts of land and most of Britain’s sea bed, is an independently run, commercial business, whose profits go to the Treasury. They are also used as the benchmark for the level of public funding for the Royal Family.
Crown Estate's net revenue profit reached £1.1 billion for April 2023-March 31 2024, up from £442.6 million for the same period in 2022/23 as it generated bumper revenue from an offshore wind farm lease tender held in 2021 called round 4.
Under the lease, companies pay for the right to build offshore wind projects with option fees across six winning projects worth approximately £1 billion per year, payable for a minimum of three years and up to 10 years.
