Electricity prices vary by nearly 4p per unit

People in north Wales, Cheshire and parts of Merseyside pay the highest rate for their electricity under the government's Energy Price Guarantee.

Customers in this region pay 36p a unit compared with the average of 34p, and the lowest of 32p, new figures show.

Over a year, those on a typical direct debit dual-fuel bill will pay £121 more than those in the cheapest region.

The energy regulator Ofgem says price differences "reflect how much it costs to transport energy to where you live".

It adds: "The charging regime… is a way to share out costs for running and maintaining the energy network."

The BBC has analysed official figures from the Department for Business, Energy and Industrial Strategy and Ofgem.

The new figures show the price per unit of electricity and gas under the Energy Price Guarantee in the 14 regions of Great Britain used by the industry. These divisions date back to the electricity board structure before nationalisation in 1947.

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North Wales and Mersey - known as ManWeb - stretches from Aberystwyth to Anglesey, and as far east as Warrington and Crewe, including Liverpool. There are around 1.4 million households in the region.

It is not the most expensive region for gas, paying just a fraction above the average of 10.3p. That still leaves a typical dual-fuel bill for electricity and gas the most expensive at £2,566 a year, higher than the typical £2,500 stated by the government for its Guarantee.

The cheapest region for electricity is the northeast of England, where 1.5 million households now pay just over 32p for each unit. Typical households in this region will pay around £2,445 a year.

Prepay customers in north Wales and Mersey and those there who pay quarterly also have the highest typical annual bills - £2,621 and £2,785 respectively - because standing charges are more and unit rates are the highest in Britain for those payment methods.

On 1 October, the day the new prices came into effect, Ben Saltmarsh of the fuel poverty charity National Energy Action Wales gave BBC Radio 4's Money Box programme his reaction.

"There is a huge question over whether that is fair. It's very significant. We have increasing numbers of people living at home with no heat or power for prolonged periods to the detriment of their health. Every penny counts," he said.

The Energy Price Guarantee will apply to Northern Ireland from November but instead of a capped price per unit there will be a discount of 17p per unit of electricity and 4.2p per unit of gas. The savings will be backdated to October.

Listen to the Money Box Energy special: Llandudno live on BBC Sounds