The areas with the least energy efficient homes, which have the highest heating bills

The Isles of Scilly has the most difficult houses to heat in England and Wales – while London properties are the easiest to keep warm.

That’s according to analysis of 23 million Energy Performance Certificates (EPCs), which measure how energy efficient a property is, by benchmark company Uswitch.

The Isles of Scilly, off the Cornish coast, ranked lowest for their above-average homes, Uswitch said.

Single-glazed windows, uninsulated walls and roofs, and electric space heaters are common problems that drive up the cost of heating inefficient homes.

Apartments and maisonettes are generally the most energy efficient homes, with multi-storey car parks and bungalows typically having greater heat losses.

Newly built homes are much more likely to have a higher EPC rating due to good insulation, and some even have solar panels and heat pumps pre-installed.

Uswitch’s ranking of 331 local governments found that Wales accounts for five of the ten local governments with the least efficient houses.

Five of the country’s best performing local authorities are based in London, led by Tower Hamlets.

This is also helped by the fact that new apartments are constantly being built in many parts of the capital, which drives up the average grade.

Natalie Mathie, Energy Expert at Uswitch.com said: “The Isles of Scilly is a beautiful part of the UK but unfortunately the older housing stock means residents lose a lot of heat through uninsulated walls and roofs.

“Take a moment to look up your home’s EPC certificate online and see where your property could be improved – the reports are incredibly detailed and will give you an estimated cost of any energy saving measures.”

How to insulate your house on a tight budget

Draft protection – saved £60 per year

The Energy Saving Trust charity says the average UK home could save £60 a year on energy bills by just protecting windows and doors against drafts, or £50 a year in Northern Ireland.

The simplest form of draft protection is thick curtains, which help block the cold from windows. This costs between £15 and £50 per curtain.

Secondary glazing – savings vary

Secondary glazing is an additional sheet of plastic or other insulating material next to a single pane window – a bit like double glazing at a low cost.

How to insulate your house on a medium budget

Install roof insulation – saved £640 a year

Someone living in a semi-detached house without roof insulation could save £640 a year by fitting their attic with 270mm insulation, according to the Energy Saving Trust.

Most roof insulation is made from large rolls of wool spun from basalt, a type of rock.

Prices vary but £25 will buy around 8-10 square meters of insulation. Insulating an entire attic can therefore cost a few hundred pounds, but most homes will recoup that money within 12 months if their energy bills come down.

Floor Insulation – £110 saved per year

For houses with timber floors, insulating your ground floor can save you more than £110 a year on energy costs for an average house, or up to £180 for a detached house.

Those figures rise to £90 and £145 a year respectively in Northern Ireland, according to the Energy Saving Trust.

As with roof insulation, this involves lifting the planks and placing the mineral wool insulation on top of the mesh between the joists. Depending on how big your house is, this can cost upwards of €100.

But if you don’t feel like hauling up your floorboards, there’s an easier way to insulate your floors — thick backed rugs, or failing that, area rugs.