King Charles has ordered heating be turned down in royal homes to cut emissions.
The detail was noted in the annual Sovereign Grant report, which outlines the royals' taxpayer-funded spending and income.
Royal treasurer Michael Stevens said inflationary pressures has also led to an increase in the prices of goods and services.
"This reporting period relates to a year in which inflationary pressures saw the price of many goods and services increase significantly for all organisations, in particular with regards to the cost of fuel and energy," he said.
The monarch's advice to turn down heating to 19 degrees is also in line with his long-term promise to cut down greenhouse gas emissions.
Last month, the monarch had ordered heating in the palace's swimming pools be turned down.
"He probably thinks the whole thing is environmentally unsound, because the palace pool water has chemicals and has to be heated. It doesn’t fit with his exercise regime or his world view,” a source told The Times.
Reuters reports Royal spending rose by 5% to $223 million (107.5 million GBP) in the last annual report, with additional income falling to $20 million (9.8 million GBP).
Queen Elizabeth's funeral had cost a total of $336 million (162 million GBP) the British Government said in May.
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