Should I fix my energy tariff or stay on a variable rate?

This is information about how the two tariff types work, not advice about which to buy. Nobody, including the comparison sites, knows where wholesale prices go next — so the honest framing is not 'which is cheaper' but 'which risk do I want to hold'. A fix moves the risk to the supplier and charges you for it. A variable tariff leaves the risk with you.

Step by step

1. Find your current unit rate and standing charge.They are on your bill and in your online account, stated separately for gas and electricity. You cannot compare anything without these two numbers, and the standing charge is the one people skip.
2. Find your actual annual usage in kWh.Your annual statement gives it. Use your own figure rather than the 'typical household' one a comparison tool assumes — the difference between a well-insulated flat and a draughty house is enormous.
3. Work out what you would pay on each tariff.Annual kWh multiplied by the unit rate, plus the standing charge multiplied by 365, for each fuel. Do it for the fixed offer and for your current rates. That is the whole comparison.
4. Check the current price cap level before deciding.Ofgem sets and revises the cap on standard variable tariffs in Great Britain; Northern Ireland has its own arrangements under the Utility Regulator. Look up the current level and the date of the next review on the Ofgem website rather than relying on a figure quoted in an article — it changes several times a year.
5. Read the exit fee.Fixed tariffs usually charge one per fuel if you leave early, though rules generally allow you to switch penalty-free in the closing weeks of the term. Check the exact wording in the tariff information label.
6. Check the length of the fix against your plans.A two-year fix is a poor fit if you may move, install a heat pump, get an electric car or change your usage pattern substantially. Match the term to how stable your life is.
7. Decide what certainty is worth to you.If a bill that jumps would genuinely destabilise your budget, a fix that costs slightly more than the cap can still be the right call. That is a household decision, not a market prediction.
8. Check the tariff type suits your setup.Time-of-use and EV tariffs need a working smart meter and a household that can shift load. They are excellent for some homes and pointless for others.
9. Take a meter reading on the day you switch.Submit it to both old and new supplier. It is the single thing that prevents a disputed opening balance later.
10. Diarise the end date.A fix that ends without action usually rolls onto the standard variable tariff. Set a reminder for about eight weeks before it expires so you can decide rather than default.

Tips

• Compare on the combination of unit rate and standing charge, never the unit rate alone — a low unit rate with a high daily charge suits heavy users and penalises light ones.
• Suppliers rarely offer their best deal to someone who has not looked. Getting a quote costs nothing and does not commit you.
• If your usage is unusual — electric heating, a home business, medical equipment — the 'typical household' comparison figures will mislead you badly.

Common mistakes

• Treating a fix as a bet you can win — You are buying certainty, not beating the market. Judging the decision afterwards by whether prices happened to fall makes it impossible to decide sensibly the next time.
• Ignoring the standing charge — It is payable whatever you use, so for a low-usage household it can be most of the bill and it changes the ranking of tariffs completely.

If it doesn't work

Questions people ask