King Charles and Prince William could face £10 million bill to upgrade estate homes under new energy rules

Hundreds of homes at risk of falling short

A Guardian investigation found that almost nine in 10 domestic properties across the duchies of Cornwall and Lancaster, as well as the Sandringham estate, have EPC ratings of D or lower. More than 100 homes on the inherited estates of Charles and William already fail the legal minimum for landlords, with one in five of a large sample rated F or G.

That leaves the two estates exposed to a costly overhaul. The likely bill, up to £10 million, reflects the scale of the work needed on ageing cottages, farmhouses and country houses, many in rural areas where insulation upgrades can be difficult and expensive.

Environmental messaging meets hard reality

The findings carry an awkward edge for both men. Charles and William have long been praised for speaking up on environmental issues. If their estates fall short of the new standards, that reputation will be tested in public.

One tenant, living in a home where coal-fired stoves provide the only heat, described the property as “archaic” and said it was not fit for the 20th century, let alone the 21st. The complaint points to a wider problem across royal rental stock: attractive exteriors, poor insulation, and bills that can bite hard in winter.

Royal finances leave room for spending

The duchy of Cornwall, created in 1337 to provide income for the heir to the throne, has long enjoyed tax advantages that ordinary landlords do not. Available reports say it operates with profit margins of about 60% and is not burdened by several taxes faced by other property owners.

That financial cushion may sharpen scrutiny. The estates have already launched public-facing language about becoming a “world-leading impact organisation”. The harder task is the one hidden behind the front doors: wiring, insulation and heating systems in hundreds of lived-in homes.

With the 2030 deadline approaching, the question is no longer whether the upgrades are needed. It is how quickly the royal estates move — and how much of the bill they are willing to absorb.