By 2025, all newly rented properties must have an Energy Performance Certificate - which grades homes on energy efficiency - of C or above.
Research from planning insights platform LandTech found only 39% of private rental properties in London currently meet that threshold. However, this is slightly better than the national figure of 36%.
Meanwhile, only 54% of London social housing meets the new requirement.
The vast majority of new builds are graded C or above, but 5% are still not compliant.
Landtech estimates the total cost to bring all rentals in London up to category C to be £15.4 billion. Its co-founder Jonny Britton said he hopes the rush to insulate and improve properties will lower tenants’ bills.
“While it will be a cost burden to landlords, our hope is that the rush to insulate and improve below C rated properties gives a boost to trades specialising in new boilers, heat pumps and windows, resulting in a reduction in energy bills for tenants,” he said.
However, Britton added that he was concerned about the cost to local authorities in upgrading social properties.
“Despite almost half of all social housing being below the proposed compliance levels, we’re hugely encouraged that social housing (whether local authorities or housing associations) has a 15 percentage point lead on private rental stock in terms of having a higher per centage EPC of C and above,” he said.
“The concern for the future is that cash-strapped local authorities still have much to do to reach the minimum standards, with costs likely to run into the millions in order to upgrade social rented housing stock.”
Only 32% of homes on the market to be sold are rated C or above, but the new rules will not apply to these homes.