UK energy supplier landscape

How Great Britain's domestic supply market is structured, regulated and protected when a supplier fails.

A domestic energy supplier buys energy for its customers, sets tariffs, manages meter and settlement data, sends bills and handles the account. It is not normally the company that owns the electricity wires or gas pipes serving the property.

Great Britain has a competitive retail market regulated by Ofgem. A household can usually choose separate suppliers for electricity and gas, a dual-fuel supplier for both, and a separate company for exported electricity.

Northern Ireland has a different market and regulatory framework. The description below concerns England, Scotland and Wales.

Supplier, network and generator are different roles

Several organisations can be involved at one address:

Role	What it does
Energy supplier	Tariff, billing, customer account and retail contract
DNO	Local electricity network and connection decisions
Gas distribution network	Local gas pipes and emergencies
Transmission/system bodies	High-voltage or high-pressure networks and system balancing
Generator	Produces electricity
Meter and data agents	Install, maintain or process meter data under industry arrangements
Export supplier	Pays for eligible metered export

Changing energy supplier does not change the local network operator. A power cut, damaged service cable or generation-connection application is therefore not dealt with in the same way as a billing complaint.

The consumer brand can also differ from the legal licensee. One group may operate several brands, acquire another supplier’s customers or use a separate company for installation and finance. The tariff information and bill should identify the company that holds the supply contract.

How the market reached its current shape

Domestic supply opened to competition in the 1990s. The former regional electricity businesses consolidated into six large, vertically integrated groups commonly called the Big Six: British Gas, EDF Energy, E.ON, npower, ScottishPower and SSE.

New suppliers entered in greater numbers after 2010. Ofgem and the Competition and Markets Authority promoted switching and investigated whether competition was working effectively. The original Big Six then changed: E.ON absorbed npower’s retail business, and OVO acquired SSE’s domestic retail operation.

The phrase “Big Six” is now ambiguous. It can mean the six historical groups or simply the six largest suppliers at a later date. A current market-share table should use an Ofgem reporting date rather than the old label.

As at 22 July 2026, the large domestic groups commonly shown at the top of Ofgem’s market-share data are Octopus Energy, British Gas, E.ON Next, OVO, EDF Energy and ScottishPower. Their order and percentages change between Ofgem reporting periods.

Large and smaller suppliers

All domestic suppliers need the relevant Ofgem licence and must follow the applicable licence conditions. Size does not create a separate category of consumer protection.

Large suppliers may have broader meter support, specialist teams and more tariff combinations. Smaller suppliers may focus on price, service, renewable purchasing or a particular digital model. Neither description establishes which will be cheaper or easier to deal with for a specific household.

Market-share and “number of suppliers” figures need care. Ofgem’s datasets have reporting lags, and counts can differ depending on whether they include electricity-only companies, gas-only companies, dormant licences, brands or legal suppliers. A dated Ofgem chart is more reliable than a timeless claim that there are a particular number of choices.

For households with solar, storage, an EV or a heat pump, the relevant market can be narrower than the licensed-supplier count. A supplier may not support the meter, device integration, export arrangement or tariff combination the property needs.

The 2021–22 supplier failures

The wholesale-price shock exposed weak business models and inadequate financial resilience. The National Audit Office recorded that 29 suppliers failed between July 2021 and May 2022, affecting nearly four million households.

Those are historical figures tied to a defined period, not a current failure rate. The NAO concluded that Ofgem had not done enough before the crisis to ensure suppliers could withstand a sustained shock, although the transfer arrangements kept customers supplied.

Bulb was too large for the ordinary Supplier of Last Resort route and entered a special administration regime. Most other failed suppliers were handled through the normal transfer process.

The episode explains why a cheap tariff is not the only market consideration and why modern supplier regulation pays more attention to capital, liquidity and customer-credit balances.

Financial-resilience rules now

Ofgem has since introduced a more detailed financial-resilience framework. It includes minimum capital and liquidity expectations, supplier capital targets and capitalisation plans for companies below target. The regulator also oversees the treatment of customer-credit balances and Renewables Obligation liabilities.

Ofgem’s 2026 financial-resilience report provides a dated snapshot. For March 2026 it reported aggregate domestic-supplier capital well above the aggregate regulatory target, while 21 of 24 assessed suppliers were above their individual capital targets. Three were below and subject to the regulator’s capitalisation-plan process.

That finding is encouraging but not a guarantee. It is a sector position as at March 2026, published before this page was reviewed on 22 July 2026. Capital can change and an individual supplier can still fail. Ofgem does not offer consumers a simple public “safe supplier” score that should replace checking current regulatory information.

What happens if a supplier fails

Loss of a supplier does not stop gas or electricity flowing. The network and meter remain in place.

Ofgem normally uses the Supplier of Last Resort process to appoint another licensed supplier. The practical sequence is:

The failed supplier stops trading.
Ofgem asks other suppliers for proposals and appoints a replacement.
Customer accounts move to the replacement supplier.
The new supplier explains the tariff and how credit balances will be handled.
Once the transfer is established, the customer can compare and switch in the usual way.

Customers should take meter readings and download bills and statements if still accessible. They should not cancel a Direct Debit solely because of a social-media report before the official instructions are clear, since the account may still need to settle a final balance.

Domestic credit balances are protected under the appointed arrangement, although transfer and reconciliation can take time. Debit balances do not disappear. The detailed treatment depends on Ofgem’s direction and the replacement supplier’s process.

The costs that an appointed supplier cannot recover through the transferred accounts may be claimed through industry arrangements and ultimately spread across bills. SoLR protects continuity and balances; it does not make supplier failure cost-free.

The role of the price cap

The price cap limits unit rates and standing charges on domestic default tariffs. It does not guarantee that a supplier’s wholesale purchasing strategy is profitable, cap a household’s total bill or apply to every fixed and smart tariff in the same way.

This tension mattered during the crisis: suppliers could face rapidly rising wholesale costs while customer prices adjusted on the regulatory timetable. Financial-resilience rules and hedging oversight therefore sit alongside the retail price cap rather than being replaced by it.

The cap changes every three months and is not a useful permanent measure of market size or health. Current cap rates belong on Ofgem’s live pages and in tariff comparisons made for a particular date.

Technology is changing the retail market

The traditional supplier sold one unit rate and read a meter occasionally. Smart meters and half-hourly settlement allow suppliers to price electricity by time and, in some products, control or reward flexible devices.

That creates several overlapping markets:

ordinary import tariffs
static time-of-use and dynamic import tariffs
device-managed EV, battery and heat-pump offers
SEG (Smart Export Guarantee) and commercial export tariffs
flexibility and virtual-power-plant services

The company importing electricity need not be the export payer, equipment installer or flexibility provider. However, commercial terms may link them. A premium export rate can require the same import supplier; a device tariff can give the supplier exclusive control rights; a flexibility contract can prevent participation through another aggregator.

The supplier landscape should therefore be assessed contract by contract, not as a single league table.

How to use market data safely

For a current decision:

Verify the legal supplier and live tariff offer.
Use Ofgem’s dated market-share and retail indicators for scale and trend.
Check current Citizens Advice and Ofgem service data separately from price.
Model import, export and flexible-load terms using the home’s own data.
Treat ownership, size and historic market share as context rather than guarantees.

This approach avoids two common errors: assuming a large brand owns the network, and assuming a small supplier is either automatically risky or automatically better value.