Should I switch to a fixed-rate energy tariff?

The decision turns on one comparison: the fixed rate on offer against the price cap that governs standard variable and prepayment tariffs. The price cap does not apply to fixed-term tariffs, so a cap rise does not reach a household inside a fix, and a cap fall does not either³. Independent guidance puts the switching threshold at no more than 40% more expensive than the current price cap⁵.

Most fixed deals run 12 months, with 12, 24 and even 36 month terms available, and most carry exit fees for each fuel if the contract is left early⁶. Suppliers must contact a household 42 to 49 days before a fixed-term tariff ends, which is the window in which the next decision is normally made⁸.

What a fixed-rate tariff actually locks in

The guarantee is narrower than the name suggests. A fixed-rate tariff locks in the price per unit of energy and the standing charge for the duration of the contract, protecting the household from changes in energy prices during the fixed term¹. It does not lock in the total bill, which moves with how much energy is used¹. A cold winter, a new appliance or a change in working patterns all change what is paid, even though the rate has not moved.

The components are worth separating. The unit cost of energy and the daily fee are fixed; the amount charged is the energy used multiplied by the unit cost, plus the daily fee¹⁰. A household that understands its annual consumption in kilowatt hours can therefore work out what a fixed deal will cost with reasonable accuracy, and a household that does not is comparing headline rates without knowing the bill they produce.

There is a second, quieter feature of a fix: the price is the same each day, at any time of day¹¹. That matters for households weighing a fix against a time-of-use tariff, where the whole point is that electricity costs different amounts at different hours. A fix is the opposite trade: one flat rate in exchange for giving up the ability to shift load into cheaper windows.

For energy independence, the fix is a hedge, not a source of supply. It changes what a household pays for grid electricity and gas, and it does nothing about where that energy comes from or whether the household could run without it. A household with solar panels and a battery has more options than one without, because it can reduce the units it buys in the first place, but the tariff decision itself remains a contract about price.

Fixed versus the price cap: how to judge the deal

The price cap sets a limit on what suppliers can charge customers on standard variable and prepayment tariffs⁴. It does not limit the total bill, only the rates that produce it¹². Fixed tariffs, business energy contracts, heat networks and heating oil all sit outside it³. That is the whole basis of the comparison: a fixed deal is judged against a cap that would otherwise govern the household's rates, and the gap between the two is the price of certainty.

The cap has moved sharply in recent years. Rapid increases in wholesale energy prices from mid-2021 onwards led to a 54% increase in the price cap in April 2022¹³. Since summer 2022 the cap has been set every quarter rather than every six months, in response to high and volatile wholesale prices¹⁴. A quarterly cap means a variable tariff household sees its rates reviewed four times a year, which is the volatility a fix is designed to remove.

Ofgem has consulted on updating how the cap level is set for single-rate customers, those who pay the same price for electricity regardless of when they use it¹⁵. That is a technical change to the mechanism rather than a change to who the cap covers, but it is a reminder that the cap is an administered price, not a market one, and that its level is a policy decision as much as a cost calculation.

The practical test is straightforward. A fixed deal priced below the cap is cheaper than doing nothing, and independent guidance confirms such deals exist, worth checking for households still paying out-of-contract rates¹⁶. A fixed deal priced above the cap is buying insurance, and the question becomes whether the household values that certainty more than the difference. Around 11 million households are on a standard variable tariff or one they have not chosen, which is the population for whom this comparison is live⁹.

The switching threshold: no more than 40% above the cap

The most commonly quoted rule of thumb is that a fixed-rate deal is worth considering at no more than 40% more expensive than the current price cap⁵. The figure is a threshold, not a target: it marks the point beyond which the premium for certainty is generally judged too high, not a level at which every household should switch.

The same 40% figure appears in a different context that is worth keeping separate. On Economy 7, a household would have to use more than 40% of its electricity during the night to make switching worthwhile¹⁷. The number is coincidental, and the two tests measure different things: one compares a fixed rate with a cap, the other compares night usage with day usage. Neither substitutes for the other.

Applying the threshold requires knowing the current cap level and the fixed rate on offer, both expressed in the same units. Unit rates and standing charges are the figures to compare, alongside whether prices are fixed or can change, the length of any fixed-term contract, payment methods available, customer service and support, and any additional benefits or incentives¹⁸. A deal that clears the 40% test on price but carries a long term and a high exit fee is not automatically the better choice.

Consumer understanding of exit fees is weaker than it should be. Ofgem research found that 57% net of consumers could identify that exit fees may still apply to a fixed contract even when moving to another deal with the same supplier¹⁹. That is a gap that matters at the point of comparison, because a household that assumes switching within a supplier is free may misjudge the true cost of the deal it is signing.

Typical fixed terms: 12 to 18 months, and the options on offer

Fixed deals offer peace of mind by locking in the price of energy for the length of the contract, typically 12 months²⁰. Longer terms exist: 12, 24 or even 36 months are available⁶, and fixed energy tariffs usually run 12 to 24 months²¹. A fixed rate tariff normally has a minimum term of 12 months²². Ofgem's own consumer research tested 12 month fixed term, 24 month fixed term and standard variable options, which reflects the shape of the market households actually choose from¹⁹.

The habit that independent guidance recommends is switching every 12 to 18 months²³. That is slightly longer than the typical contract, which means the practical rhythm is to review at the end of each fix rather than to hold one for its full advertised life and drift. Suppliers are required to contact a household 42 to 49 days before the end date of a fixed-term tariff, informing them of what happens next⁸. Switching with 21 to 49 days left on the current tariff avoids spending a few days or weeks on the current supplier's standard variable rate²⁰.

What happens at the end of a fix is the part households most often misjudge. With a fixed rate, the household rolls onto the provider's standard variable rate when the tariff ends²⁴. Suppliers will probably move a household to their standard variable tariff when a fixed plan ends, although some may offer the chance to move to another deal². The rollover is not a penalty imposed for inaction so much as the default position, and it is the reason the notice window matters.

What switching costs you, and what it does not

Moving from a variable rate to a fixed tariff should not cost anything, because there is no contract to break²⁵. The costs sit on the other side of the decision. Most fixed tariffs include exit fees for each fuel, payable if switching before the end of the contract⁷. Ofgem guidance confirms that a household may have to pay its previous supplier an exit fee if it was on a fixed rate tariff and chose to leave before it ended²⁶. Independent guidance is blunter: leaving a fixed contract early may mean an early exit fee⁶.

The standard test is to compare the exit fee with the savings available on the new deal, since moving to a cheaper tariff could still save money overall¹⁸. Choosing a tariff with low or no exit fees, in case circumstances change, is advice offered for exactly this reason²⁷. Some fixed-rate tariffs charge a fee if the contract is left before it ends, and the amount varies by supplier and by fuel¹⁸.

There are protections on the switching process itself. If a switch is not completed within a set period, the new supplier must pay the household £40, and the same £40 applies if the energy supply is switched by mistake²⁶. Prepayment meter customers face a separate limit: switching is blocked if more than £500 is owed in gas or electricity²⁰.

The wider point is that switching is a repeatable process, not a one-off. Reviewing the tariff regularly to ensure it is the best deal, and being aware of any exit fees, is the pattern that keeps the cost of the contract visible²⁸. A household that fixes and forgets has bought certainty and then stopped checking whether it was worth the price.

Where a fixed tariff fits an energy-independent household

A fixed tariff is a price contract, and price is only one of the dependencies a household carries. The grid still delivers the energy, a supplier still bills for it, and gas still heats most homes. What a fix changes is exposure to wholesale price movements during the term, and what it leaves untouched is everything else: the physical supply, the standing charge that applies whatever the usage, and the fact that the household cannot generate its own power unless it has installed generation.

That is why the tariff decision sits alongside, rather than instead of, the measures that reduce units bought. A household with solar panels and a battery can shift consumption into its own generation and export the surplus, and fixed tariffs are valid for a certain period, typically 12 months, after which a new option has to be found²⁹. The export side of that arrangement is a separate contract with its own terms, and it is worth reading alongside the import decision rather than after it.

Some tariffs are explicitly built for households with controllable load. OVO's Charge Anytime requires the customer to already be signed up to a home energy tariff, whether fixed or standard variable, which shows that a fix and a smart-charging add-on are not mutually exclusive³⁰. The same logic applies across the market: a fixed import tariff can sit underneath a time-of-use or EV arrangement, and the household's independence comes from the combination rather than from the fix alone.

There is also a supplier-side dependency worth naming. Fixed tariff customers with smaller scheme savings were affected by changes involving 100 Green, Fuse Energy, Good Energy, Home Energy and Tulo Energy, suppliers funding only one of two schemes³¹. A fixed rate is only as durable as the company standing behind it, and the financial position of the supplier is part of the risk a household takes on when it signs a 12 or 24 month contract.

For a household weighing the decision, the honest summary is this: a fix removes price risk for a defined period, at the cost of a premium over the cap and an exit fee if circumstances change. It does nothing for supply independence, and it does not reduce consumption. Households that want to cut what they buy need generation, storage or load-shifting, and the tariff is the wrapper around those choices rather than a substitute for them.