A significant number of landlords – 15% of the 1,000 asked by Shawbrook Bank in a survey – report having no knowledge of the energy efficiency rule changes coming in the next few years.

And 25% of landlords said they have ‘little to no’ awareness of the changes.

From 2025, all newly rented properties must have an energy performance certificate (EPC) rating of at least ‘C’. This deadline is extended to 2028 for existing tenancies.

Failure to comply will lead to a property becoming unrentable.

The lender’s research also shows that 36% of landlords say their properties were built before 1940, and, in London, the South West, Scotland and Wales specifically, 40% of landlords reply in this manner.

Analysis from Habito published late last year found the average cost of upgrading a property from an EPC ‘D’ rating to ‘C’ is £6,155.

Meanwhile, The Mortgage Works has found that over half of landlords who need to invest to comply with the new rules have considered selling.

Shawbrook Bank sales director Emma Cox says: “The true extent of what this legislation could mean for the market has not yet been properly realised. Inaction could see a considerable percentage of the private rental sector declared unrentable or unsellable within a matter of years if landlords don’t take important steps now.

“Making changes to improve a property’s energy efficiency rating will help to improve the overall energy efficiency of the UK housing stock and to assist the government in meeting the ambitious net-carbon zero targets set out earlier this year.

“But on a more direct level, making the improvements ahead of the impending 2025 deadline will ensure that properties remain commercially viable for the short and long term for landlords. Putting off making necessary changes could leave landlords exposed to extended void periods when their property can’t be rented out while works are being completed.

“Mortgage lenders, and key players in the market, have a big role to play in supporting landlords by helping them to understand the new legislation, the potential impact this could cause and how to take action, if required.

“Our research indicates a clear gap in landlord’s understanding of how the changes will impact them and their current yields. As well as these risks to landlords, renters may also be put in an even worse position as they compete for a smaller number of properties that are rated C or above after the 2025 deadline.”