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Can you delay the start of a new fixed energy tariff?

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UKPublished 6 October 2026 · Written by BuyMeWhiskey Editorial Team · How we check facts

Sometimes, but you cannot assume a new fixed tariff can be held for a convenient future date. The supplier’s terms and the switching timeline control when the new contract starts. Compare the existing fix’s end date, any exit charge and the new tariff’s start arrangements.

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Ask the new supplier for the exact contract start date and check your current tariff’s end date and exit fee before agreeing to the switch.

Read Ofgem switching guidance

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A fixed tariff is a contract, not a price promise

A fixed energy tariff normally fixes the unit rates or standing charges for the agreed term, but the contract still has a start and end date. If you arrange a switch months before your existing fix ends, the supplier may have a specific process for scheduling the transfer. You should not assume you can choose any start date you like. Ask for the date in writing and retain the confirmation.

Compare one-year and two-year fixes properly

A longer fix buys certainty but can lock you in if prices fall or your circumstances change. A shorter fix gives you another chance to choose a tariff sooner but can expose you to future market prices. Compare the estimated total cost over the period, exit charges and the value you place on certainty. Do not compare only the headline unit rate because standing charges can materially affect the total.

When leaving the existing fix

You may be able to switch without an exit fee during the final part of a fixed contract, but the exact rules depend on the tariff and supplier. Check your current terms. If an early-exit fee applies, include it in the switching calculation. A cheaper new tariff is not automatically cheaper after a large termination charge.

A future price-cap change is not a guarantee

The regulated cap applies to eligible default or standard variable tariffs, not to every fixed deal. Headlines about an expected cap rise or fall are therefore not a reason by themselves to break a fixed contract. Compare the exact tariff offers available to you and the dates they apply. Ofgem’s current cap information is useful for context, but your fixed-tariff contract remains the key document.

Deferring a start date

If the supplier offers a future start date, confirm whether the price is locked until then or whether it can change before the switch. Also ask what happens if the switch date moves because of a metering or registration problem. A written confirmation should state the tariff, expected start date and any conditions.

Choose based on your household’s flexibility

If you expect to move home, install an electric vehicle, change heating or reduce consumption, flexibility may be more valuable than a slightly cheaper fixed rate. A two-year fix that looked attractive for today’s usage can be a poor fit after a major change in the household. Keep the decision tied to your actual usage rather than a market prediction.

Check the contract dates before choosing a new fix

The important dates are the end of the present fix, the date the new supplier accepts the switch, and the date the new supply begins. They can differ, so a household should not assume that arranging a tariff early means the new rates are immediately active. A supplier may also set a switching window or require the existing contract to be near its end before the transfer is completed.

For a one-year or two-year decision, compare total expected cost with the value of certainty. A longer fix can reduce exposure to later price changes, while a shorter fix preserves more flexibility if the household moves or expects its consumption to change. Exit charges matter because a cheaper tariff can become more expensive once the cost of leaving the present contract is included.

Economy 7 needs its own comparison

A household using Economy 7 should compare peak and off-peak consumption rather than relying on one headline electricity price. Overnight storage heating, immersion heating and timed vehicle charging can make off-peak use substantial. The relevant calculation is annual kWh in each period, multiplied by the corresponding rates, plus standing charges and any other contract costs.

Ofgem says customers can switch suppliers and that a previous supplier may charge an exit fee where the customer leaves a fixed tariff early. The new supplier tells the customer when it plans to complete the switch. That process is why a written start date is more useful than an assumption based on the day the deal was advertised.

Worked example

Illustrative example: A household estimates that its current tariff would cost £1,650 over the next year. A new fixed tariff is estimated at £1,560, but leaving the existing contract early would cost an illustrative £100.

Illustrative new-tariff saving before exit cost: £1,650 − £1,560 = £90.
Illustrative exit charge: £100.
Net result of switching early: £90 − £100 = −£10.

On those assumptions, switching early is £10 worse over the comparison period. The exact calculation should use your supplier’s current tariff, estimated consumption, standing charges and contractual exit rules.

The figures in this example are hypothetical. Compare them with the tariff’s actual contract dates, exit charge and quoted annual cost before drawing a conclusion.

The useful comparison is the net cost alongside the contracted dates, because an exit charge can reverse a headline saving.

The useful lesson is to compare the whole switching cost rather than only the advertised rate. If the existing fix has no exit charge, the same method can be repeated using the new tariff’s standing charges and estimated annual consumption. A written commencement date then tells you when the comparison actually starts to apply.

Can I pick the exact date a new energy fix starts?#

A fixed-tariff start date is not always immediately flexible. The supplier controls the switching process and its contract terms may limit the start date. Ask for the agreed date in writing and check whether the price is guaranteed until then. Retain the tariff quote and contract statement used in this comparison. A tariff arranged before your existing fix ends still needs a confirmed commencement date from the new supplier.

Is a two-year fix better than one year?#

It depends on the value you place on certainty and your view of future prices. A longer fix can reduce exposure to future price changes but can also make you less flexible if rates fall. For this tariff question, save the agreed start date and supplier correspondence. The relevant comparison is annual cost after exit fees, standing charges and the dates of both contracts.

Should I leave a fix early to avoid a price-cap rise?#

Usually you need to calculate the actual cost, including any exit fee and the timing of the new tariff. A price-cap forecast is not the same as a guaranteed future bill for your household. For a fixed-term comparison, retain the pricing terms and the contract dates. Economy 7 should be tested against your actual day and night consumption rather than its label alone.

Can my new supplier change the fixed tariff before the switch?#

Ask what the contract says. Some offers lock a price when accepted; others may have conditions. The written tariff terms should tell you what is actually fixed and from what date. Keep the supplier’s written tariff terms with the calculation. A longer fixed term buys price certainty but also reduces flexibility if your household changes.

Do standing charges matter when comparing fixes?#

For low-use homes, standing charges can outweigh the headline unit rate. Your total cost is driven by both unit rates and standing charges, so a lower unit price can still be more expensive when fixed daily charges are higher. Record the agreed switching date because a delayed start may leave the existing tariff running while the new contract waits to begin.

What if the energy switch is delayed?#

Contact the supplier and keep the expected start date, meter details and correspondence. Ask which tariff applies while the switch is delayed and whether the supplier will honour the originally agreed terms. Save the supplier’s explanation of any delay alongside the expected commencement date. The price cap affects default tariffs, not a properly fixed contract during its agreed term.

Where can I compare energy tariffs fairly?#

Ofgem provides consumer guidance on switching and the price cap. Use current supplier terms and your actual usage when comparing offers, and check whether any quote includes estimated rather than actual consumption. For the final comparison, retain the quote and the usage figures used to produce it. A written start date is especially useful where the old and new contracts overlap in the switching process.

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Sources

Figures were checked against these sources before publication. If a rule changes, we update the page and show the new date.

General information, not personal financial advice. Rules depend on your circumstances; check the official source or speak to a regulated adviser before acting.