Customers who move to the cheapest energy tariffs are facing eye-watering price rises once those deals end, research has found. But you can stay one step ahead of these hikes by switching suppliers.

You could be paying up to 53% more for your energy when your deal expires and your supplier moves you onto its standard variable tariff, according to analysis from small energy firm Octopus.

The big six energy firms were all among the 10 worst offenders for hiking prices when cheap tariffs end – though smaller independent provider First Utility was the worst overall, with annual costs leaping by £394 for a typical household.

Octopus Energy has accused suppliers of failing to make the scale of future price rises clear to their customers when they first sign up – a claim echoed by Conservative MP and Commons Energy and Climate Change Committee member Glyn Davies, who has branded firms' behaviour "deceptive".

Octopus founder Greg Jackson is calling on the industry to display "multi-year" price estimates when customers sign up, so those who don't switch every 12 months can see costs over the long term and therefore make "informed choices" when choosing a supplier.

The best way to avoid huge price rises when your fixed tariff ends is to switch again. MSE's free Cheap Energy Club will help you find the best deal based on your household usage – and if you register by 8pm tonight (12 September), you'll be able to join our market-beating collective switch.

Martin Lewis
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Which suppliers have the biggest hikes?

Octopus Energy compiled the following figures by comparing each firm's best-value one-year fix (offered within the last six months) with its current standard tariff, based on national average usage for a typical dual-fuel household.

10 biggest price rises from fixed to standard tariff
Energy Supplier Annual cost on cheapest tariff Annual cost on standard tariff Percentage increase
First Utility £746 (Fixed July 2017 – Online Only) £1,140 (First Variable) 53%
Npower £724 (Price Fix July 2017) £1,072 (Standard Energy) 48%
EDF £727 (Energy Simple Fixed May 17) £1,068 (Standard Variable) 47%
Extra Energy £753 (Fresh Fixed Price Oct 2017 v1) £1,095 (Variable Price v1) 45%
Scottish Power £729 (Fixed Price Energy June 2017) £1,059 (Standard) 45%
British Gas £720 (HomeEnergy Exclusive June 2017) £1,031 (Standard) 43%
Co-op Energy £758 (Fix For Longer Sept 2017) £1,073 (Pioneer Variable) 42%
Sainsbury's £747 (Fixed Price June 2017) £1,031 (Standard) 38%
SSE £752 (1 Year Fixed v8) £1,028 (Standard) 37%
E.on £758 (MSM fixed 1 Year Collective March 2016)
£1,031 (Energy Plan paperless) 36%
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