HOUSEHOLDS face an average hike in their energy bills of more than £260 over the next three months as hundreds of fixed tariff deals come to an end.

Market experts urged consumers to shop around now to avoid lapsing by default onto the major gas and electricity providers' more expensive standard variable tariffs.

It is estimated that some 413,000 households across the UK will be affected as fixed deals run out.

An analysis by price comparison website, Compare the Market, found that 227 fixed rate tariffs are ending between July and September 2019.

On average, that is is expected translate into bills for heating and electricity costing £262 more on average in the third quarter of 2019 than they did in the period from April to June.

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The quarter-to-quarter hike is substantially higher than it was earlier this year, with average bills going up by £67 in the first quarter of 2019 compared to the last three months of 2018.

If customers do nothing, the major energy companies will bank an estimated £109 million extra in what has been dubbed an "inertia windfall".

Peter Earl, head of energy at comparethemarket.com, said: “It rarely pays to be loyal to an energy company.

"Once the terms of a fixed rate tariff come to an end, customers could be automatically rolled onto an uncompetitive standard or default tariff, the shocking cost of which could see energy companies rake in an additional £109 million over the next three months.

"Energy company bosses will be planning on this revenue windfall that comes off the back of the energy price cap, which saw the bills for households on standard and default tariffs increase by £117 on average per year from April 1.

"These are of course customers who were already savvy enough to be on a fixed term tariff in the first place, but unless you stay on top of your bills it is an easy trap to fall into.

"These figures demonstrate the importance of knowing the date that your tariff is coming to an end and searching and switching to a more competitive tariff to ensure you’re getting the best deal available.”

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When the energy price cap came into force on January 1 this year, the regulator Ofgem predicted that it would save 11 million people an average of £76 a year.

Households on so-called default tariffs - such as standard variable tariffs - were among those expected to benefit from the initiative, which set a maximum price per unit of energy.

It meant that while heavier users of gas and electricity would still may more than energy-efficient households, suppliers could not charge customers on default tariffs more than 17 pence unit of electricity or four pence per unit of gas.

However, the cap was labelled a "con" by some consumer campaigners in February amid claims that energy providers were scrapping their cheapest deals and adjusting prices upwards to make the most of the cap threshold.

Ofgem also raised the cap in April, blaming the need to balance out higher wholesale costs for suppliers.

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Consumer champions have warned that thousands of deal-savvy customers who have been cushioned from increases until now as a result of having signed up to cheaper fixed tariff deals may not have as many options to choose from this time around even if they are shopping around.

Research by Which? found that the number of energy deals costing less than £1,000 a year for medium users had dropped from 77 in January to just six by early February.

Rik Smith, an energy expert at price comparison website, uSwitch.com, said doing nothing would still leave customers worse off.

He said: "There were over 50 price rises during 2018 which added nearly £900 million to household energy bills, prompting almost six million people to switch supplier.

"Many switched to a fixed price deal to escape the vicious price hikes, but with so many of those plans ending over the summer, now is the time to switch again.

"If consumers do nothing they will be rolled onto a suppliers' worst value deal - a Standard Variable Tariff. But these plans can cost as much as £380 more than the cheapest deals on the market right now.

"Instead, households can switch penalty-free up to 49 days before their fixed plan ends, and lock in cheap energy prices for another year or longer."

A spokesman for Energy UK, the trade association for the British energy industry, said: “All suppliers have been facing steeply rising costs which are outside their direct control, however customers can still find a good deal by calling their existing supplier or shopping around.

"As our figures have revealed, switching reached a new high in 2018 – with close to half a million customers making a move last month.

"We hope consumers will continue to take advantage of the ever-growing competition and choice and significant savings that are available by either contacting their existing supplier or shopping around for the right deal for them, whether that’s a green tariff, cheaper deal or better customer service.”