For some cash-strapped families, failing to make the move now could plunge them into fuel poverty before the end of the year.
That may sound dramatic, but with soaring inflation pushing the average British adult's weekly outgoings up by more than £50 over the past six months, it is a very real fear.
Recent moneysupermarket.com research revealed that heating costs place the biggest strain on the household finances for a fifth of the population.
And with some 22% of those who responded to the survey admitting that their cash reserves are already stretched to breaking point, bigger energy bills could easily push them over the edge - especially given the size of the expected price hikes.
How much are costs going to rise by?
Scottish Power has already announced its next price increases, due to come in on August 1.
These will add 19% to the cost of gas and 10% to the cost of electricity, pushing the average cost of an annual bill for 2.4 million customers up by £175.
Industry insiders believe that British Gas, which has just launched two long-term fixed rate deals that are substantially more expensive than current standard charges, will announce plans to increase its prices in line with these deals before the end of the month.
The contract that allows customers to fix their prices until June next year, for example, is at a premium of 19% on current charges, while the deal that runs until March 2013 is 25% dearer.
And other energy providers will undoubtedly be quick to follow suit.
That's why it is vital for anyone keen to protect themselves from bigger energy bills to switch to a fixed-rate plan with one of the other providers yet to change their tariffs now.
Scott Byrom, utilities manager at moneysupermarket.com said: "Now really is the time to get on to the best priced energy tariff for your usage level and area you live.
"Bearing in mind historical energy market price rises, it's highly likely the other energy providers will follow suit.
"I urge everyone worried about the cost of their bills to act quickly as the best priced products are unlikely to be available for long."
Encouragingly, the number of people using moneysupermarket.com to search for a better value deal jumped by a massive 1,264% in the days following the Scottish Power announcement.
However, there are still millions more Britons yet to take action.
Is a fixed-rate energy deal right for me?
A fixed-rate plan is not the cheapest option. Tariffs of this kind are more expensive than standard deals to reflect the price-hike protection offered.
However, with further increases in energy costs just round the corner, paying a bit more for a fix now could well save you a lot in the longer term.
For the many households already struggling to cope financially, knowing that their energy bills are fixed for at least the next 12 months will also provide valuable peace of mind.
And even though they are not the cheapest deals on the market - the best variable online tariffs cost about £930 a year - you may still be able to lower your annual energy spend by switching to a competitive fixed-rate plan.
Britons who have never switched energy providers in the past, for example, could currently save as much as £382 a year by swapping to the current cheapest fixed deal - the Fix Saver v2 tariff from EDF Energy - at £1,009 a year, fixed until September 2012.
Even someone on a typical standard tariff costing about £1,150 a year could make an instant saving of almost £150.
Other attractive options include npower's Go Fix 6 at an average annual cost of £1,013.80.
Cheap fixes like this are sure to get pulled soon, though, so time is of the essence if you want to benefit.
What do I need to watch out for when choosing a fixed-rate tariff?
There are a number of things to consider when choosing a fixed-rate energy deal.
Obviously, the amount you will pay per year is the first thing to look at.
However, you also need to consider how long you want to fix for - the length of these plans varies between one and five years - and whether you are prepared to accept exit fees.
These are charges imposed by some suppliers to ensure that customers do not simply ditch their fixed tariffs the moment prices start to fall (although they should not affect you if you move house during the term).
When it comes to the length of the deal, you will generally pay more to fix for longer but save more, should prices continue to increase.
If you believe that prices could start to go down again and are concerned about fixing for that reason, it is also worth looking at capped deals, which limit on how much your energy can cost while allowing the amount to fall should the providers begin lowering their prices.
These too tend to be a bit more costly due to the added flexibility, though.
Finally, remember that it's the price you pay for units of energy that is fixed, not the actual size of your bill.
Consequently, switching to a fixed tariff is not a reason to start using more gas and electricity, especially if you are on a tight budget.
Please note: Any rates or deals mentioned in this article were available at the time of writing.
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