King Charles and Prince William face £10m energy upgrade bill for royal estates

King Charles and Prince William could face a combined bill of up to £10 million to bring rental properties on their private estates up to the UK government's planned energy-efficiency standard of EPC band C by 2030, according to a Guardian investigation published on 16 August 2026.

The government confirmed in its Warm Homes Plan, published on 21 January 2026, that all private landlords will be required to reach EPC C or equivalent in their rental properties by 2030 — a significant step up from the current minimum of band E, set under the 2018 Minimum Level of Energy Efficiency standard. An Energy Performance Certificate, or EPC, is a document introduced in 2007 that scores a property's energy efficiency from A (best) to G (worst). The government has said the change could lift up to half a million households out of fuel poverty.

The Guardian examined more than 700 domestic EPCs across three royal estates — the Duchy of Lancaster, the Duchy of Cornwall and the Sandringham estate — and found that 630 properties would fail to meet the proposed C standard. Almost nine in ten domestic properties across the three estates carry ratings of D or lower. More than 100 homes sit in bands F or G, the two lowest categories.

The picture varies by estate. On the Sandringham estate in Norfolk — bought by Queen Victoria in 1862 and covering about 8,000 hectares (19,000 acres) — 99 per cent of rental properties rated D or below. The Duchy of Lancaster, established in 1265 to provide a private income for the sovereign and spanning about 18,000 hectares (44,000 acres), stood at more than 90 per cent. The Duchy of Cornwall, founded in 1337 to generate income for the heir to the throne and covering about 55,000 hectares (135,000 acres), came in at about 80 per cent.

The precise number of domestic properties across the three estates is unclear because the estates do not publish lists of their landholdings, though the figure is believed to exceed 1,200. King Charles inherited the Sandringham estate and the Duchy of Lancaster from his mother, Queen Elizabeth II, after her death in 2022. No inheritance tax was paid on either estate, because assets passing between monarchs are exempt. Prince William, as heir to the throne, holds the Duchy of Cornwall.

Upgrading each property could cost up to £10,000, according to the Guardian's analysis. Landlords who continue to rent out homes without carrying out the required work could face fines of £30,000 per property. The government's consultation response, published on 21 January 2026, sets a per-property investment cap of £3,500 for landlords to meet the higher standard, though the Guardian's cost estimate for the royal estates appears to assume work exceeding that cap — for instance, where properties need substantial insulation or heating-system upgrades.

Nationally, just over half of all rental properties in the UK currently fall below band C, meaning the royal estates are broadly in line with a country-wide challenge. A 2024 investigation by Channel 4's Dispatches and the Daily Mirror had previously found that many privately rented properties on the Duchy of Cornwall carried the worst energy-efficiency ratings, foreshadowing the broader findings published this week.

What gives the story its bite is the paperwork behind it. These are not palaces or publicly occupied royal residences but private rental homes — cottages, farmhouses and town houses let to tenants at market rates, on landholdings whose accounts are scrutinised by the National Audit Office and the Public Accounts Committee. The estates operate as working property portfolios. Under the new rules, they will be treated like any other landlord's portfolio.

Neither Buckingham Palace nor the Duchy of Cornwall has commented publicly on the findings. The government's EPC C requirement is scheduled to take effect in 2030.