The short version
General information, not advice
- A fix holds your unit rate and standing charge for the term, usually 12 to 24 months.
- A variable tariff moves every quarter with Ofgem's price cap.
- The cap covers variable and default tariffs, not fixes.
- Fixes usually carry an exit fee; variable tariffs usually don't.
This is general information about UK energy tariffs. It is not personal financial advice.
Steps or a flat line
On a variable tariff your price moves every three months, when Ofgem resets the cap. Drawn over time, that’s a staircase. A fix replaces the staircase with a flat line for the length of the deal. Move the slider to set a fix and see where the cap would have to go for it to pay off.
From October 2026 to March 2027, the fix costs £860 and the cap, on our central forecast, £955.
For the fix to cost less than the cap over its 12 months, the cap would have to average more than £1,530 a year from April 2027 to September 2027. Nobody knows yet where it will be.
Illustrative, not a quote. Annual cost at Ofgem’s typical use of 2,500 kWh of electricity and 9,500 kWh of gas, direct debit, Great Britain average. Earlier quarters are restated on today’s typical use, so they read lower than the figures published at the time. The band is our forecast for January – March 2027, from market prices on 2 October 2026: our estimate, not Ofgem’s figure. Sources: Ofgem’s published caps, restated in our price cap manual; Ofgem, changes to the price cap, October to December 2026, checked 25 September 2026.
See it step by step
Steps or a flat line
Step 1 of 6
Steps or a flat line
On a variable tariff your price moves every three months, when Ofgem resets the price cap. Drawn over a year, that is a staircase.
A fix holds your unit rate and your standing charge for the term, usually 12, 18 or 24 months. That replaces the staircase with a flat line.
Example: the steps here are invented to show the shape. Nobody knows where the real cap will go.
Figures from the Switch4Good guide, Fixed vs variable tariffs explained, checked 4 October 2026: the prices £1,780 and £1,720 and every step are examples, not quotes. The 49-day switching window is Ofgem's rule.
What a fix does
A fixed tariff holds your unit rate (the price per kWh) and your standing charge for the term, usually 12, 18 or 24 months. If wholesale prices rise, your rates don’t. If they fall, your rates don’t either. Your direct debit can still change, because it follows how much you use.
Suppliers price a fix on what they expect wholesale prices to do. When they expect a rise, a fix can be cheaper than today’s cap. When they expect a fall, it can cost more.
What a variable tariff does
A variable tariff has no set end and no fixed price. The common one is the standard variable tariff, which is where you land when a fix ends and you don’t choose another deal. Ofgem’s price cap sets the most a supplier can charge per kWh and per day on it, and resets that every quarter.
The cap limits rates, not bills: use more and you pay more. Ofgem sets a different cap in each of fourteen regions and by payment method; the rates for your region are here. Variable tariffs usually have no exit fee, so you can leave whenever a better deal appears.
Exit fees and the end of a fix
Fixed tariffs often carry a fee to leave early, usually charged per fuel. Put yours in the box above the chart and the break-even moves to show what leaving would have to save to cover it.
Ofgem rules allow customers to switch penalty-free in the final 49 days of a fixed contract. Suppliers must contact you before your contract ends to explain your options.
Before you choose, check four things: the exit fee for each fuel, the end date, what tariff you move to afterwards, and whether you have to give notice.
Comparing like with like
Compare unit rates and standing charges separately, on the same payment method and for the same region. Direct debit is usually cheaper than paying on receipt of a bill. Prepayment has its own cap. Work from your annual kWh, which is on your bill or in your supplier’s app, rather than from your monthly payment.
When wholesale markets swing hard, fixes can be withdrawn or priced well above the cap. That happened in 2021 to 2023. Calmer markets bring them back.
Where to get help
Citizens Advice on energy supply (energy helpline 0808 223 1133) and Ofgem’s advice for households are both free and independent. Switch4Good Limited is a commercial business and not a charity.
Your energy bill checklist
Twelve things to look at on the bill in front of you.
- Find the unit rate and the standing charge for each fuel on the bill.
- Check whether the reading the bill is based on is an actual reading or an estimate.
- Compare the reading on the bill with what the meter shows today.
- Check the MPAN (electricity) and MPRN (gas) on the bill belong to your address.
- Check which tariff you are on and whether it has an end date.
- Check whether an exit fee applies if you leave before that date.
- If you are on a standard variable tariff, check the rates against the cap for your region.
- Check the VAT rate applied to a domestic supply.
- Check any credits, discounts or government support are shown.
- Check the billing period runs from where the last one stopped, with no gap and no overlap.
- Check your direct debit against what the bill says you are actually using.
- Check whether anyone in the household would qualify for the Priority Services Register.
Common questions
Is a fixed tariff always cheaper?
No. A fix is priced on what suppliers expect wholesale prices to do. When they expect prices to fall, fixes can cost more than the cap.
Can my fixed tariff price change?
Your unit rate and standing charge stay the same for the term. Your direct debit can still change if your usage does.
Does the price cap apply to fixed tariffs?
No. It applies to standard variable and default tariffs.
Can I leave a fixed tariff early?
Yes, but exit fees may apply unless you are within 49 days of the contract end date.
What happens when my fix ends?
You're usually moved to your supplier's standard variable tariff, which the cap covers, unless you choose another deal.
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