Not while you're on a fixed deal — on a variable one, they can, but they owe you 30 days' warning first.
It depends entirely on which type of tariff you're on. A fixed-term tariff locks in your unit rates and standing charges for the length of the term — your supplier can't change them mid-contract without your consent. A standard variable tariff (SVT) is different: the supplier can change prices, but only after giving you at least 30 calendar days' advance notice, and you're free to switch away penalty-free during that window to avoid the change entirely.
| Tariff type | Can price change mid-term? | What protects you |
|---|---|---|
| Fixed-term tariff | No | Rate is contractually locked until the term ends |
| Standard Variable Tariff (SVT) | Yes, with notice | At least 30 days' advance notice, plus a penalty-free window to switch away |
| Fixed tariff at renewal (rolled onto SVT) | N/A — you're moved to a new tariff type | SVT rates are capped by Ofgem's quarterly price cap |
The confusion usually comes from what happens at the end of a fixed deal. If you don't actively choose a new tariff, you're typically rolled onto your supplier's SVT — this isn't a mid-contract change, it's what happens once your original contract has genuinely ended, and the rate you land on is capped by Ofgem.
Under the standard licence condition governing unilateral contract variations, a domestic supplier making a price change or other unfavourable change to your variable tariff must:
The price cap applies specifically to Standard Variable Tariffs and prepayment meters, not fixed deals. It's reviewed roughly every three months and sets a maximum unit rate and standing charge — it caps what you pay per unit, not your total bill. If you use more energy, your bill can still rise well above the "typical household" figure quoted in the cap announcement, entirely within the rules.
What happens when my fixed-term energy tariff ends? If you don't actively choose a new deal, you're typically rolled onto a standard variable tariff (SVT), which is subject to Ofgem's price cap. The cap limits the unit rate and standing charge suppliers can charge on SVTs, but it doesn't cap your total bill — your bill still depends on how much energy you use.
How much notice must a supplier give before a price rise? Under the standard licence condition covering unilateral contract variations, suppliers must give domestic customers at least 30 calendar days' advance notice of a price increase or other unilateral change to their variable tariff, sent as a standalone notification, giving you time to switch away before it takes effect.
Use Kibbo's Telecoms & Utilities tools to check your notice period and draft your dispute or switch request.
Explore Telecoms & Utilities tools →