How much notice must my supplier give before a price rise?

The 30-day rule applies to a variation the supplier chooses to make. It is not the mechanism by which the Ofgem price cap moves. The cap is reviewed and reset on a fixed quarterly cycle, and the new level is announced in advance of the period it covers, so a cap-driven change arrives on a published timetable rather than through a notice letter.

The cap rises 4% from 1 October 2026, taking a typical annual dual fuel bill from £1,663 to £1,723 for the period to 31 December 2026³. That figure describes a household with typical usage in Great Britain paying by direct debit, not a ceiling on any individual bill.

What Ofgem's rules require of suppliers

The notice rule sits inside a wider set of licence and regulatory obligations. Suppliers must cut their prices to the price cap level or below that Ofgem sets⁷, and from early 2026 suppliers will have to offer at least one "low standing charge" tariff⁸. Ofgem introduced new requirements for existing firms in January 2021, including a new financial responsibility principle that made it a legal requirement for suppliers to manage costs that would be mutualised in the event of supplier failure⁹.

On billing and credit, Ofgem credit refund rules require suppliers to reimburse customers on request unless there is a good reason not to¹⁰. Ofgem rules protect customers in debt where a supplier wants to install a prepayment meter¹¹. An energy supplier cannot charge domestic or microbusiness consumers for energy used, or for charges, more than 12 months old due to the supplier's error¹².

The cap itself is a legal instrument with limits on what Ofgem can do with it. Under the Act, Ofgem cannot set different cap levels for different suppliers and must protect default tariff customers¹³. That constraint matters to the notice question: because the cap applies across suppliers, a cap-driven change is a market-wide event announced by the regulator, while a supplier's own tariff restructuring is the kind of change the 30-day notification rule is designed to catch.

Compliance is monitored rather than individually policed. Ofgem will be closely monitoring supplier compliance and will continue to take firm action against suppliers who fall short of their requirements⁵. That is an enforcement posture, not a case-handling service, and the next section explains why the distinction matters to a household with a complaint.

The price cap: how changes are set and announced

The price cap sets a maximum amount that suppliers can charge per unit of energy for customers on default tariffs, as well as a limit on the daily standing charge¹⁴. It applies to standard variable and prepayment tariffs¹⁵. It is not a cap on the total bill: a household that uses more than the benchmark pays more, and one that uses less pays less.

The benchmark annual consumption levels, described in the methodology as the 'm' figures, are to be specified in a statement at least 25 days before the start of the charge restriction period¹⁶. That is the formal publication deadline for the numbers behind the headline. The headline itself is announced ahead of the period it applies to, which is why the 1 October 2026 change was known before it took effect.

Recent cap movements show the range. Ofgem announced a 2% rise of the energy price cap for the period covering October to December 2025¹⁷. The January to March 2024 price cap was 5% higher than the previous cap¹⁸. The current cap makes an energy bill for a dual-fuel home with typical usage in Great Britain who pay by direct debit around £1,758 for 1 January to 31 March 2026⁴. These describe different cap periods, and the £1,723 figure is the one dated to the period from 1 October 2026.

The cap rises 4% to £1,723 for a typical dual-fuel home

The 1 October 2026 change is a 4% increase, moving the typical annual figure from £1,663 to £1,723³. Energy bills are rising 4% from October, energy regulator Ofgem announced on Wednesday 26 August¹⁹. The increase is driven mainly by higher wholesale gas prices²⁰.

For context on how far the cap has travelled, the price cap limited the average annual household bill to £1,717 for October to December 2024, which is higher than pre-energy crisis levels and a 10% rise, an additional £149²¹. Between 1 January and 31 March 2025 the energy price cap was set at £1,738 per year for a typical household²². The current price cap for average households on dual fuel direct debit increased to £1,849 in April 2025 due to higher wholesale prices²³.

Prepayment customers are capped separately. The prepayment cap level increased to £1,803, a £113 (7%) increase compared to the previous level, for the 1 April to 30 June 2025 period²⁴.

The figures are not directly comparable across rows: some describe direct debit dual fuel customers, one describes prepayment customers, and the benchmark consumption assumptions behind them have been reviewed. What they show is the direction and scale of movement a household on a default tariff has absorbed.

When the cap is reviewed and when new rates take effect

Ofgem updates the price cap every three months⁴. Every 3 months Ofgem reviews and sets a level for how much an energy supplier can charge for each unit of energy and daily standing charge⁹. That is the current cycle.

Older Ofgem documents describe a different one. Updates to the cap level occur in February and August in a given year, which respectively apply for cap periods starting in April and October²⁵. Every six months Ofgem works out how much it costs a supplier, on average, and revises the cap level²⁶. Those documents describe the six-monthly cycle that applied before the quarterly cycle came in, and the quarterly statements are the ones that govern current periods.

The forward review dates are published. Ofgem's review for the January to March 2027 cap period is due on 25 November 2026⁵. The review for April to June 2027 is due on 23 February 2027, and the review for July to September 2027 is due on 26 May 2027⁵. Each review sets the level that applies for the following quarterly period, so a household can see the next announcement date well ahead of the bill change.

The practical sequence for a household is: the review is published, the new unit rates and standing charges take effect on the first day of the following quarter, and the bill reflects them from that date. The cap change is not a notice event in the 30-day sense, because the timetable is fixed and public in advance.

Deemed contracts: the 'unduly onerous' limit on out-of-contract rates

A deemed contract arises when a household occupies a property and uses energy without having agreed a contract with the supplier. Ofgem's rules state that the terms of deemed rate contracts should not be "unduly onerous"⁶. Ofgem's own test for meeting that standard is that suppliers can ensure contracts are not unduly onerous by making sure that the profit it derives from deemed rate customers is not significantly higher than the profit derived from contracted customers⁶.

The gap between deemed and contracted rates can be wide. Ofgem has seen examples where deemed rate customers are charged more than double the rate of customers on contracts⁶. In one case study, the standing charge on the deemed contract was nearly 14 times higher than the consumer could have achieved on contract⁶.

There is a separate information duty. The licence conditions (7.7) set out an obligation for suppliers to send information regarding the deemed contract rates, explaining the prices and informing the customer of cheaper prices⁶. The Energy Ombudsman will consider whether it was appropriate for a supplier to place a customer on a deemed rate contract, or whether supplier error or omission left the customer on high deemed contract prices for longer than necessary⁶. That is a procedural question, distinct from the price level.

For a household's energy independence, the deemed contract is the weakest position available: no agreed term, no fixed rate, and a rate that Ofgem's own evidence shows can be more than double a contracted one. Moving onto an agreed tariff, whether fixed or variable, is the step that removes the exposure. The tariff rules and consumer protections page sets out what suppliers must offer, and closed and withdrawn tariffs covers the position when a chosen tariff is no longer available.

What Ofgem does and does not do for individual customers

Ofgem does not investigate individual complaints about energy suppliers or network operators, including heat network suppliers and operators. Its stated position is that it generally does not intervene in individual disputes between consumers and energy businesses, including heat suppliers and operators²⁷. Its work is rule-setting and enforcement across the market: the back-billing condition, for example, prevents a supplier charging domestic or micro-business consumers for energy used more than 12 months before the date of the bill where the customer is not at fault²⁷.

What it does instead is monitor and enforce. Ofgem will be closely monitoring supplier compliance and will continue to take firm action against suppliers who fall short of their requirements⁵. It also publishes scheme-specific contact addresses rather than a general consumer complaints line: feedback@ofgem.gov.uk for Boiler Upgrade Scheme administration matters²⁸, and ecogbis_compliancequeries@ofgem.gov.uk for questions related to supplier compliance under the Energy Company Obligation²⁹.

The route for an individual dispute runs through the supplier first. A complaint to the supplier is the first step where a customer considers they have not been given reasonable notice². If that does not resolve it, the Energy Ombudsman is the next step, and it will consider the appropriateness of placing a customer on a deemed rate contract or leaving them there through supplier error or omission⁶.

On affordability, the support available is set out by Ofgem. If you are struggling to pay for energy or think you may get into difficulty, you can ask your supplier to agree a payment plan, a payment break or a reduction, to review payments and debt repayments, and to give access to hardship funds³⁰. Suppliers can agree a payment plan, payment break or reduction³¹. Ofgem rules protect customers in debt where a supplier wants to install a prepayment meter¹¹, and suppliers must reimburse credit balances on request unless there is a good reason not to¹⁰.

The dependence that remains is structural. The cap protects a household on a default tariff from the worst of the market, but it does not remove exposure to wholesale prices, and it does not give the household control over when the rate changes. A fixed tariff transfers that timing risk to the supplier for the term; a variable or default tariff leaves it with the household. The energy tariffs pillar sets out the full range of contract types, and tariffs and household energy independence covers what each does for a home's exposure to the grid and the market.