How to Read a Gas and Electricity Bill

A domestic energy bill is built from a small number of parts: a charge for each unit of gas or electricity you use, a daily standing charge that applies whether or not you use anything, and the meter details that show how the consumption figure was worked out. Behind those parts sit the supplier's own costs: wholesale costs for the energy itself, network costs for the wires and pipes, operating, debt and industry costs, the supplier's earnings, policy costs, and VAT at 5%¹. The same bill also carries rights that many households never read: a 12-month limit on catch-up charges, and automatic or claimable compensation when a supplier or network misses a required standard.

The figures that decide what you pay are the unit rate, the standing charge and the consumption in kWh. What those figures are depends on the type of energy you use, the type of meter installed, and how you pay your bill, for example by direct debit³. This page walks through each line of a typical bill, then explains the protections that sit around it: back billing rules, guaranteed standards of service, power cut compensation, and what Ofgem does when a supplier does not follow the rules.

The unit rate, the standing charge and the meter details

Every bill starts with the same three pieces of information, and each one is worth checking rather than skimming past.

The unit rate is the price per kWh of gas or electricity. It is the number that moves most when tariffs change, and it is the figure to compare when looking at fixed and standard variable tariffs. The standing charge is a fixed daily amount that covers the cost of supplying your home regardless of how much energy you use; it is explained in full on standing charges. The meter details identify which meter the readings came from, its serial number and, on most bills, the tariff name applied to those readings.

What sits behind those numbers is a chain of costs. Ofgem sets out the components used to calculate bills: wholesale costs, meaning the cost a supplier pays to buy energy; network costs; operating, debt and industry costs; the supplier's earnings; policy costs; and VAT at 5%². On top of those, the final figure depends on the type of energy you use, for example gas or electricity, the type of meter installed, and how you pay your bill⁴. A household on an Economy 7 meter, for instance, is billed differently from a single-rate meter, which is covered on Economy 7 and restricted meter billing.

The meter details matter because they are the evidence base for everything else. If the meter serial number on the bill does not match the meter in your home, or the readings are marked as estimates, the consumption figure may not reflect what you actually used. How suppliers must read meters, and how often, is covered on meter readings and estimated bills.

What your meter readings reveal about energy use in kWh

The consumption figure on a bill is expressed in kWh, and it is calculated from the meter readings: the difference between the reading at the start of the billing period and the reading at the end. Gas meters record consumption in cubic units, which are converted to kWh on the bill, while electricity meters record kWh directly.

The critical distinction is between a bill based on an accurate reading and one based on an estimate. An estimated bill can be far from reality in either direction, and the consequences of a long run of estimates are what the back billing rules exist to address. A smart meter removes most of that risk: with one installed, you do not need to submit meter readings yourself, and you get bills based on accurate meter readings and not estimates⁸. That single change is one of the most effective ways to keep a bill honest, because it removes the gap between what the supplier assumes and what the home actually uses.

For households without a smart meter, the practical position is that the readings on the bill are only as good as the information the supplier holds. Checking whether the readings are marked "actual" or "estimated", and comparing the end reading against the meter itself, tells you whether the kWh figure is real or modelled. If a bill is based on an estimate, the consumption figure will be corrected later, and the correction can be large if the estimates have drifted. What estimated readings mean in practice is explained on estimated bills explained.

The 12-month cap on backdated energy bills

A back bill is what happens when a supplier has not accurately charged you for energy you have already used, and then sends a bill for it later¹⁰. The classic case is a household that receives no bills for a period, perhaps because of a metering problem or an administrative error, and then gets a single large demand covering years of consumption.

The protection against that is Ofgem's back billing rule: you do not have to pay for energy you used more than 12 months ago where you have not had an accurate bill for it before, or where a direct debit was set too low¹⁰. Citizens Advice puts the same rule in plainer terms: under back billing rules, your supplier cannot usually send you a bill for energy you used more than 12 months ago⁵. The rule is not just guidance. It is written into suppliers' licence conditions as SLC 21BA, restricting suppliers from charging for energy used more than 12 months ago, with limited exceptions¹².

The conditions attached to that sentence are the part worth reading carefully. The limit applies where you have not had an accurate bill, a statement of account, or a direct debit set too low¹⁰. In other words, the rule protects households from a supplier's own failure to bill, not from charges the supplier has already raised correctly. The full detail, including how to challenge a catch-up bill, is on back billing rules and catch-up bills.

Exceptions to the 12-month rule

The limit has exceptions, and they mostly turn on the customer's own conduct.

Ofgem lists the behaviour that removes protection: you will have to pay for energy used more than 12 months ago if you have acted unreasonably, for example by stopping your supplier from billing you accurately, including by blocking access to your meter, by ignoring requests for payment from your supplier, or by stealing electricity or gas¹⁰. Citizens Advice adds a further case: the rules do not apply if the supplier sent you a bill before the year passed and you did not pay it, in which case the supplier can still charge you⁵.

The scope of the rule is narrower than many assume. The back-billing authorisation condition applies only to domestic and micro-business consumers, which means non-domestic consumers outside the micro-business category are not covered¹³. Within Ofgem's consumer outcomes work, only the meter read requirement applies to all non-domestic consumers, with the backbilling condition applying to microbusinesses¹². The size of a catch-up bill outside full protection can be substantial: one case handled by the Energy Ombudsman involved a microbusiness receiving a bill for three years of electricity charges billed on a deemed rate¹⁴.

Two further exclusions come from heat networks, which are regulated separately. Where charges are recovered through a service charge, they are not covered by the 12-month back-billing limit¹³. And in the heat network consumer protection guidance, the limit does not apply where the consumer was obstructive in refusing a meter reading, where the consumer had a responsibility to provide a meter reading and did not, or where the consumer had a responsibility to manage, report broken or fix parts of the heat network and failed to, resulting in unpaid consumption¹⁵.

Suppliers must put billing errors right

If a bill is late, incorrect or missing, the first step is to contact your energy supplier¹⁶. The list of problems a supplier must handle runs wider than most households realise: late, incorrect or missing bills; back billing; being overcharged; a faulty meter; poor customer service; and refusing to refund credit from your account¹⁶.

The responsibility sits with the supplier because the supplier holds the meter data, sets the tariff, calculates the charges and issues the bill. Where a supplier has been charging on a deemed rate, the price is often higher because suppliers are not able to purchase gas or electricity in advance and instead must pay the market rate at the time energy is consumed¹⁴. That is a supplier-side commercial reality, not something the customer controls, and it is one reason a deemed-rate bill can look wrong even when the arithmetic is correct.

The position is different for residents who pay a landlord or site owner by meter readings or estimates, for example in some park homes and leased accommodation. Those residents cannot choose their own energy supplier or switch suppliers themselves, and they cannot make a complaint directly to the energy supplier if they do not have a contract with them¹⁸. What they can do is see the bills and contract between the landlord or site owner and the energy supplier¹⁸. Households in that position can check whether switching is possible on switching energy supplier and switching in a park home.

The limit under direct debit and prepayment arrangements

For direct debit customers, a back bill rarely arrives as a single demand. Instead, the supplier might increase your payments, using the extra amount to pay off what you owe over a few months⁵. Suppliers are also expected to review your current payments and debt repayments²⁰, so a rising direct debit can be either a routine review or the quiet collection of older charges; the difference matters, and it is worth asking which one it is. How to challenge a change is covered on how to challenge your supplier's direct debit increase.

For prepayment customers, the mechanics differ because there is no bill to backdate in the usual sense: energy is paid for before it is used. The government support schemes of recent years showed how the two prepayment populations are treated differently. Under the Energy Bills Support Scheme, smart prepayment meter customers saw the discount credited directly to their smart prepayment meters each month, while traditional prepayment customers received vouchers via SMS, email or post, redeemable at PayPoint or the Post Office²¹. In Northern Ireland, customers with a direct debit arrangement received the payment directly to their bank account, while those on standard credit without a direct debit, and those on prepayment keypad meters, received vouchers²³.

Prepayment households also face a distinct risk: running out of credit. A private member's bill introduced in December 2022 proposed requiring energy companies to allow a grace period before disconnecting customers with prepayment meters who have run out of credit, and to require energy companies to offer debt management support to all customers²⁴. The practical protections around running out of credit are on emergency credit on a prepayment meter and self-disconnection.

Guaranteed service standards and who oversees them

The Guaranteed Standards of Performance (GSOP) are set by Ofgem and specify what an electricity distribution network operator must pay a customer, or a relevant authority as appropriate, if they fail to meet specified standards of performance²⁵. On the supplier side, the same framework applies: the supplier GSOPs set minimum supplier service standards, with consumers automatically compensated if they are breached¹².

The mechanism is deliberately simple. Guaranteed Standards set out minimum performance standards which all energy suppliers must meet and, when they do not, automatic payments are issued to the affected consumers²⁷. No claim form is needed for the supplier standards; the payment follows the failure. Ofgem has been extending the framework to smart meters, with a statutory consultation in August 2025 planning new definitions relevant to the Guaranteed Standard smart meter proposals, including smart meter, in-home display, first time smart meter appointment, and not operating as intended²⁷.

One point of structure matters when reading supplier performance data: subsidiary brands such as white label brands are included in the supply group that is responsible for their customer service operations²⁸. So a bill from a lesser-known brand is backed by the standards and the record of the larger group behind it, not a separate small company.

Payments for power cuts and the qualifying thresholds

For unplanned power cuts, the compensation is built from fixed payments that rise with the length of the interruption. You get an extra £45 for every additional 12-hour period without electricity⁶.

Ofgem's worked examples show how the payments stack up:

These examples apply to unplanned electricity cuts⁷. For businesses, the figure for planned and unplanned power cuts is £120⁷. For unplanned gas cuts, you can claim £70 extra for every additional 24 hours your gas supply is off⁷. There is also a payment for repeated failures: an extra £100 if your power has gone off more than 4 times between 1 April and 31 March the following year, for homes and businesses, where each cut lasted at least 3 hours, and this one requires a claim⁷.

The amounts are not permanent. Ofgem reviews and updates the amount you will be paid for a power cut each year based on inflation⁶. To report a power cut, call 105 for free, and you will be put through to your electricity network operator⁶.

Storm compensation is paid automatically

The usual route to power cut compensation is a claim to the network operator. The exception is severe weather. When a storm is the cause, compensation is paid automatically, with no claim needed, which matters because households dealing with a storm are often the least able to chase paperwork.

The principle of automatic payment is well established elsewhere in the energy support landscape. Cold Weather Payments, for example, are paid without an application: if you are eligible, you get these payments automatically and you do not need to apply³⁰. The same logic underpins smart metering, where readings flow without the household doing anything: you do not need to submit meter readings yourself⁸.

For a household, the practical implication is to know which regime applies. After an ordinary fault, contact the network operator via 105 and claim. After a named storm, watch for the payment to arrive rather than assuming silence means nothing is owed. If a payment that should have been automatic does not appear, the complaint route is the same as for any other failure: the network operator first, then the Energy Ombudsman.

Cases where compensation is not owed

The compensation rules have exclusions, and they are worth knowing before a claim is made. For power cuts, no compensation is paid for blackouts caused by a national power shortage, for damage to electrical equipment or appliances, or for a low supply after a power cut⁶.

The guaranteed standards also do not reach every household in the same way. Residents paying a landlord or site owner by meter readings or estimates cannot access all the protections available to domestic energy customers¹⁸. Their contract is with the landlord or site owner, not the energy supplier, so the supplier-facing standards do not attach to them directly.

On the supplier side, the standards work in both directions. If a supplier owes you a refund of credit from your account and does not pay it, you could get compensation if they do not³. But the standards compensate for defined failures within defined timescales; they do not cover general dissatisfaction with a price, a tariff or a bill level. For those, the route is a complaint, not a guaranteed payment.

How Ofgem handles suppliers that break the rules

Ofgem monitors energy suppliers and network operators closely to make sure they meet the rules set out in licences, regulations and law, provide good customer service, and reply quickly to customers who contact them¹⁷. If Ofgem thinks a supplier or network operator has not met certain rules, it will start an investigation¹⁶.

Monitoring is not passive. On the price cap, Ofgem has stated it will be closely monitoring supplier compliance and will continue to take firm action against suppliers who fall short of their requirements³³. Its duties also include calculating energy suppliers' obligations under schemes such as the Energy Company Obligation and tracking performance against them, processing notifications, auditing suppliers, counter fraud work, and reporting to the Secretary of State at the Department for Energy Security and Net Zero³⁴.

Between the regulator and the household sits the Energy Ombudsman, an independent service separate from Ofgem, which handles problems with an energy supplier, an energy broker, a network operator or a heat network supplier¹⁶. Its reach extends to specialist schemes: where electricity suppliers obligated under the Feed-in Tariffs scheme do not follow the rules set by Ofgem, the Ombudsman can consider complaints³⁵. The practical sequence for a household is fixed: complain to the supplier first, and if the complaint is not resolved, take it to the Ombudsman. How to complain about a specific catch-up bill is on how to complain about a back bill.

A clear bill's role in managing your own energy use

A bill you can read is the foundation of everything else on this page. Knowing your unit rate tells you what each kWh costs, so the running cost of any appliance can be worked out, as covered on appliance running costs. Knowing your standing charge tells you the floor below which no saving can go, however little you use. Knowing your consumption in kWh, from accurate readings rather than estimates, tells you whether efficiency work is actually cutting use⁹.

What a bill cannot do is make a household independent. The unit rate is set by the supplier and shaped by wholesale costs, network costs and policy costs the household does not control². The standing charge is paid whether or not any energy is used at all. The bill's figures depend on the type of energy, the type of meter and the payment method⁴, all of which are choices within a supplier's framework rather than outside it. Even the protections described here, from back billing limits to guaranteed standards, are protections within the supplier relationship, not exits from it.

The genuine independence a readable bill offers is informational: the ability to check the arithmetic, spot a wrong charge, enforce the 12-month limit, claim the compensation that is owed, and compare tariffs on real numbers rather than marketing. That is worth something, and it is why each line of the bill deserves a minute of attention. The wider picture of how bills connect to self-sufficiency is on energy bills and energy independence.