Is YOUR town one of these 10 where homes leak the most heat? Areas with the most - and least - energy efficient properties are revealed

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The Isles of Scilly have the hardest homes to heat in England and Wales - while London properties are the easiest to keep warm.

That is according to analysis of 23 million energy performance certificates (EPCs), which measure how energy efficient a property is, by comparison firm Uswitch.

The Isles of Scilly, off the coast of Cornwall, rank lowest due to their older-than-average homes, Uswitch said.

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

Not so hot: Station Road in the Welsh village of Trawsfynydd has some of the least energy efficient homes, according to Uswitch

Flats and maisonettes are the most energy-efficient homes in general, with park homes and bungalows commonly seeing greater heat loss. 

New-build 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 authorities revealed that Wales makes up five of the ten local authorities with the least efficient homes. 

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

That is helped by the fact that new flats are constantly being built in many parts of the capital, pushing up the average score.

Natalie Mathie, energy expert at Uswitch.com, said: 'The Isles of Scilly is a beautiful part of the UK, but its older housing stock unfortunately means residents are losing 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 estimated costs for all the energy-saving measures.'

How to insulate your home on a tight budget

Draught-proofing - £60 a year saved

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

The simplest form of draught-proofing is thick curtains, which help block cold coming from windows. This costs from £15 to £50 per curtain. 

Secondary glazing - savings vary

Secondary glazing is an additional sheet of plastic or other insulating material next to a single-glazed window - a bit like double glazing on the cheap. 

The Isles of Scilly, off the coast of Cornwall, rank lowest in terms of energy efficiency due to older-than-average homes, Uswitch said.

How to insulate your home on a medium budget 

Fit roof insulation - £640 a year saved 

Someone living in a semi-detached house with no roof insulation could save £640 a year by fitting 270mm insulation in their loft, the Energy Saving Trust has said.

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

Prices vary, but £25 will buy around 8-10 square metres of insulation. Insulating an entire loft might therefore cost a few hundred pounds, but most homes will make that money back inside 12 months as their energy bills fall.

Floor insulation - £110 a year saved

For homes with timber floors, insulating your ground floor can cut energy bills by more than £110 a year for the average home, or up to £180 for a detached house.

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

Like roof insulation, this involves lifting the floorboards and putting down mineral wool insulation on top of netting between the joists. Depending on how big your house is this can cost £100 upwards.

But if you don't feel like pulling your floorboards up, there is a simpler way of insulating your floors - carpets with thick underlay, or failing that, rugs.