Up to half a million households will be hit by gas and electricity price hikes today as numerous cheap deals expire.

Some face rises of 23% which could add £186 a year to a typical energy bill (see the Cheap Gas & Electricity guide).

In total, 14 fixed, capped or discounted offers ended either yesterday or today including deals from five of the Big Six: British Gas, EDF, Eon, Npower and Scottish Power.

It is normal for many cheap offers to expire at the end of a quarter-year period but price comparison website Energyhelpline.com says it is the largest number of deals expiring in one go it has ever seen.

It estimates between 250,000 and 500,000 households will see rises as a result.

Double whammy of hikes

Most on these cheaper deals will be moved to their provider's standard tariff, which is usually the most expensive deal they have.

But they face a double whammy given households will also feel the full force of the winter price hikes of up to 9% that they had previously been shielded from.

A fixed tariff is one where the price per unit of energy used is set for the term. A cap is where the price cannot rise but it can fall. A discount deal is a reduction from the supplier's standard tariff.

Mark Todd, director of Energyhelpline, says: "1 April is a time for hoaxes but these price rises are all too real for hundreds of thousands of people.
"The tariffs being pulled had protected households against the latest round of price rises but I suppose all good things must come to an end."

The biggest rise affects customers on Eon's FixOnline 6 deal that ends today. Users will automatically be placed on the firm's EnergyOnline deal which is 23% more expensive, turning a typical £825 annual bill into a £1,011 demand.

Next worst affected are households on the EDF Annual Fix 2 deal which expired yesterday. They will pay 13% more, adding £120 a year to the typical £930 cost.

The following deals all ended yesterday or today, according to Energyhelpline, meaning anyone on them will now face a hike.

  • British Gas Price Guarantee March 2011
  • EDF Energy Annual Fix 2
  • EDF Energy Online Saver 5
  • EDF Energy Discount Plan 2
  • Eon EnergySaver R1
  • Eon Price Protection R2
  • Eon FixOnline 6
  • Npower Sign Online 17
  • Npower Web 17
  • Scottish Power Fix 'n' Flex April 2011
  • Scottish Power Capped for Free
  • Scottish Power Capped Price Energy April 2011
  • Scottish Power Price Tracker April 2011
  • Scottish Power Discounted Energy April 2011

Hit by price hike? What should you do?

Anyone on any of the above deals, or anyone else who has not switched energy tariff over the past year, is likely to be paying too much.

While the cost of a standard tariff is typically £1,100 a year, the cheapest online deals start at around £900.

To find the best tariff, compare the options available via a comparison site, although be aware you need to search separately for fixed and non-fixed deals (see the Cheap Gas & Electricity guide).

The best deals are available to those who get their bills online and pay by monthly direct debit.

When switching, remember that when a firm describes its tariff as cheapest, it's based on an average and can vary hugely depending on where you live.

The energy market is complicated so determining which is the cheapest provider for you depends on your location and how much power you use.

This is why a comparison, based on your circumstances, is key.

Further reading/Key links

Slash energy costs: Cheap Gas & Electricity
Your rights: Fight Energy Direct Debits
Boiler protection: Boiler Cover