The biggest energy companies in the UK, 2026
The UK's biggest energy companies — suppliers, generators and regulated networks — ranked by the turnover in their own filed Companies House accounts. One caveat dominates this list: energy turnover is mostly the pass-through cost of wholesale gas and power, so trading desks and financial vehicles are excluded and the figures are read with care.
What the filings show
Read this table with one number in mind: almost none of it is profit, and most of it isn't even really the company's own money. Energy-retail turnover is overwhelmingly the wholesale cost of gas and electricity bought and passed straight through to customers — so Centrica's £24.64B (it owns British Gas) and the suppliers below it measure energy bought and resold far more than business size. It's the one industry where we'd point you at the staff column and the customer numbers before the revenue.
The clearest proof is the year-on-year column: 13 of the 20 companies with comparable years shrank, several by a third or more. Nothing collapsed — wholesale prices simply fell back from the 2022–23 crisis peak, and pass-through turnover fell with them. The same mechanism inflated these figures two years ago. Octopus Energy is the conspicuous riser, still growing into the customer base it has won from the legacy suppliers.
The most comparable figures belong to the 5 regulated network operators — National Grid's transmission and distribution businesses, Cadent, UK Power Networks, National Gas — whose revenue is set by the regulator rather than the gas price. Their relative stability, against the wild swings of the suppliers, is the real shape of the UK energy system: volatile retail, steady wires and pipes.
Top 20 energy companies in the UK by filed turnover
Latest accounts filed as of June 2026 · refreshed monthly
| # | Firm | Turnover | YoY | Staff | Accounts |
|---|---|---|---|---|---|
| 01 | Centrica Multinational energy and services group Centrica plc, consolidated — owner of British Gas, the UK’s biggest energy supplier. | £24.64B | -26% | 20,290 | FY to Dec 2024 |
| 02 | Octopus Energy Energy supply and technology group Octopus Energy Group Limited, consolidated — now the largest domestic supplier by customers. | £13.68B | +10% | 10,030 | FY to Apr 2025 |
| 03 | EDF Energy Integrated energy generator and supplier EDF Energy Limited, the UK group; its retail arm (EDF Energy Customers) and nuclear-generation arm file separately. | £10.61B | -24% | 819 | FY to Dec 2024 |
| 04 | SSE generator & networks Listed energy and utility group SSE plc, consolidated — generation, transmission and distribution across Britain and Ireland. | £10.13B | -3% | — | FY to Mar 2025 |
| 05 | E.ON Next retail supplier Retail gas and electricity supplier E.ON Next Energy Limited, the group’s domestic supply arm; E.ON UK’s holding company files a smaller standalone figure. | £7.94B | -36% | 3,852 | FY to Dec 2024 |
| 06 | Drax generator Listed renewable energy group Drax Group plc, consolidated. | £6.16B | -20% | 3,243 | FY to Dec 2024 |
| 07 | OVO retail supplier UK energy and technology group OVO Group Ltd, consolidated. | £5.53B | -37% | 5,059 | FY to Dec 2024 |
| 08 | TotalEnergies Gas & Power supplier & trading Business gas and electricity supplier UK gas and power supply and trading arm of TotalEnergies. | £4.78B | -19% | 795 | FY to Dec 2024 |
| 09 | ScottishPower retail supplier Gas and electricity supplier ScottishPower Energy Retail Limited, the Iberdrola-owned group’s domestic supply arm; its trading desk files separately. | £4.69B | -38% | 932 | FY to Dec 2024 |
| 10 | Uniper UK generator UK electricity generation subsidiary | £3.51B | -43% | 651 | FY to Dec 2024 |
| 11 | National Grid Electricity Transmission network Electricity transmission network operator The UK electricity transmission monopoly; National Grid plc itself is a UK+US group not ranked here. | £2.62B | -4% | 6,102 | FY to Mar 2025 |
| 12 | National Grid Electricity Distribution network Electricity distribution network operator National Grid’s regional distribution networks (the former Western Power Distribution). | £2.48B | +35% | 7,083 | FY to Mar 2025 |
| 13 | UK Power Networks network Electricity distribution network holding company UK Power Networks Holdings Limited, consolidated — London, South East and East of England distribution. | £2.46B | +35% | 6,388 | FY to Mar 2025 |
| 14 | SEFE Energy B2B supplier Commercial gas and electricity supplier Business gas supply (the former Gazprom Energy UK); its trading affiliate SEFE Marketing & Trading is excluded. | £2.21B | -8% | 291 | FY to Dec 2024 |
| 15 | Cadent Gas network UK gas distribution network operator Britain’s largest gas distribution network. | £2.17B | -5% | 6,361 | FY to Mar 2025 |
| 16 | VPI generator Power generation holding company VPI Holding Limited — gas-fired generation. | £1.88B | -53% | 297 | FY to Dec 2024 |
| 17 | Utility Warehouse multi-utility Listed multi-utility service provider Telecom Plus plc, consolidated — multi-utility (energy, broadband, mobile) reseller. | £1.84B | -10% | 2,291 | FY to Mar 2025 |
| 18 | RWE Generation UK generator UK power generation subsidiary | £1.59B | -43% | 811 | FY to Dec 2024 |
| 19 | National Gas Transmission network Operator of Great Britain's gas network Britain’s gas transmission system operator. | £1.55B | -2% | 2,244 | FY to Mar 2025 |
| 20 | Utilita retail supplier Pay-as-you-go energy supplier Prepayment-focused domestic supplier. | £1.17B | -17% | 542 | FY to Mar 2025 |
The firms we can't rank
Energy's excluded names are trading desks and global majors whose filed turnover would mislead more than it informs.
- National Grid plc — a UK+US group (~half its turnover is American) — its UK network entities are ranked instead of its global figure
- SEFE Marketing & Trading — a commodity-trading house (£6.3B) — turnover is traded volume, not an operating energy business; its supply arm SEFE Energy is ranked
- Shell / BP UK — integrated oil majors report globally; no comparable UK energy-supply turnover line
- Ovo, Octopus pre-group filings — group consolidations are ranked; the many operating subsidiaries are excluded to avoid double-counting
- The energy "turnover" caveat — across this sector, filed turnover is dominated by wholesale-energy pass-through and was inflated by the 2022–24 price crisis — it is the weakest size proxy of any industry we rank
How this list is built
Source. The latest annual accounts each firm filed at Companies House. Where a firm files consolidated group accounts, the group figure is used; the entity ranked is named under each firm. Where a firm filed a transition period longer or shorter than twelve months (flagged in the Accounts column), the table shows the filed figure but the firm is ranked on its annualised equivalent.
Who counts as an energy company. Domestic and business energy suppliers, electricity and heat generators, and regulated transmission/distribution networks — tagged by type. We exclude commodity trading and marketing desks (turnover is traded volume, not an operating business), zero-staff financial vehicles, and integrated oil majors (Shell, BP) that report globally with no comparable UK energy-supply line.
Scope and the pass-through caveat. Rankings use each group's UK filing, deduplicated to one entity per group. National Grid is represented by its UK network companies, not its UK+US plc. Above all: filed turnover in energy retail is dominated by wholesale-cost pass-through and was inflated by the 2022–24 price crisis — it is the weakest size proxy of any sector we rank, and the network operators' regulated revenue is the only genuinely stable figure here.
Cadence. Rebuilt monthly as new accounts land. Spot a energy company we've missed or misread? Tell us — the methodology only works if it's challenged.
Quick answers
- What is the biggest energy company in the UK?
- By filed turnover, Centrica (£24.64B, owner of British Gas), then Octopus Energy and EDF. But read on: in energy, turnover is a poor proxy for size — most of it is the wholesale cost of gas and electricity passed straight through to customers.
- Why did almost every energy company's turnover fall?
- 13 of the 20 companies with comparable years shrank by more than 5%. That's not decline — it's wholesale prices falling back from the 2022–23 crisis peak. Because retail energy turnover is mostly pass-through cost, it rose and fell with gas prices rather than with the businesses themselves.
- Why are some huge energy 'turnovers' excluded?
- Commodity trading desks book the full value of energy they trade as turnover — CNOOC's UK marketing arm filed £5.5B on 22 staff, and SEFE Marketing & Trading £6.3B. Those are traded volumes, not operating energy businesses, so they're excluded. Network operators (the wires and pipes — National Grid, Cadent, UK Power Networks) are tagged separately: their regulated revenue is the most stable and comparable figure in the sector.
- Why isn't National Grid number one?
- National Grid plc is a UK+US group — around half its turnover is American. Ranking its global figure would overstate its UK energy footprint, so we rank its UK network entities (electricity transmission and distribution) instead. Shell and BP are excluded for the same reason: they report as global oil majors with no comparable UK energy-supply line.