Top 6 UK Energy Suppliers Ranked By Customer Share

These UK energy suppliers are ranked by their share of domestic electricity customers in Great Britain, using 2025 data from Ofgem’s State of the Market Report. The list covers the six largest suppliers serving household electricity customers.

British Gas leads the ranking at 27%, with Octopus close behind at 25%. Together with E.ON, the top three suppliers account for 65%, showing how much of this market is concentrated among the leading names.

Uk Energy Suppliers Ranked By Share of Domestic Electricity Customers

How We Ranked These 6 Domestic Energy Suppliers in Great Britain

• Ranked by: share of domestic electricity customers (%), 2025 data. This is the only measure used for the order.
• Data source: OFGEM STATE OF THE MARKET REPORT, retrieved 2026-11-08.
• Included: Domestic energy suppliers in Great Britain, from Ofgem retail market indicators.
• Excluded: Business-only suppliers.
• Ties: none in this list. If two entries had the same figure, share of domestic gas customers would decide.
• Figures: reported exactly as published by the source. CleanTech Journal does not estimate or adjust them; comparisons between entries are our own calculation from these figures.

1. British Gas: 27 %

British Gas holds 27% of domestic electricity customers, putting it in first place and 2% ahead of Octopus in second. Within this six-supplier ranking, it accounts for 29.7% of the list total. Ofgem includes British Gas among the six largest suppliers in Great Britain’s domestic market. In its Q3 2025 customer service data, Ofgem recorded 1.2 complaints per 100 customer accounts for British Gas, with 59% resolved by the end of the next working day. British Gas was also one of three large domestic legacy suppliers named by Ofgem as having submitted a Consolidated Segmental Statement under the earlier reporting rules.

2. Octopus: 25 %

Octopus ranks second with 25% of domestic electricity customers, 2% behind British Gas and 12% ahead of E.ON. It represents 27.5% of the list total. Ofgem highlights Octopus as the only supplier among the big six that increased its market share in both electricity and gas. Compared with Q3 2024, the regulator says Octopus gained approximately 2% in electricity and 1% in gas market share. Ofgem’s Q3 2025 complaints table recorded 0.6 complaints per 100 customer accounts for Octopus, while 47% of its complaints were resolved by the end of the next working day.

3. E.ON: 13 %

E.ON has 13% of domestic electricity customers, placing it 12% behind Octopus and 3% ahead of OVO. It makes up 14.3% of the list total. Ofgem counts E.ON among the six largest suppliers in Great Britain’s domestic market. In the regulator’s Q3 2025 customer service data, E.ON recorded 0.9 complaints per 100 customer accounts, matching the industry average of 0.9. Its share of complaints resolved by the end of the next working day was 60%, compared with an industry average of 52%.

4. OVO: 10 %

OVO ranks fourth with 10% of domestic electricity customers. It sits 3% behind E.ON and 1% ahead of EDF, which is the smallest gap between neighboring suppliers in this ranking. OVO accounts for 11% of the list total. Ofgem lists OVO as one of the six largest suppliers in Great Britain’s domestic market. In Q3 2025 customer service data, OVO recorded 1.5 complaints per 100 customer accounts, and 67% of complaints were resolved by the end of the next working day.

5. EDF: 9 %

EDF holds 9% of domestic electricity customers, putting it 1% behind OVO and 2% ahead of Scottish Power. That gives EDF 9.9% of the list total. Ofgem includes EDF among the six largest suppliers in Great Britain’s domestic market. In the regulator’s Q3 2025 customer service data, EDF recorded 1.2 complaints per 100 customer accounts, and 76% were resolved by the end of the next working day. EDF was also one of the three large domestic legacy suppliers that had submitted a Consolidated Segmental Statement under the earlier reporting rules.

6. Scottish Power: 7 %

Scottish Power ranks sixth with 7% of domestic electricity customers, 2% behind EDF. It represents 7.7% of the list total. Ofgem lists Scottish Power as one of the six largest suppliers in Great Britain’s domestic market. In Q3 2025 customer service data, Scottish Power recorded 1.4 complaints per 100 customer accounts, with 64% resolved by the end of the next working day. Scottish Power was also one of the three large domestic legacy suppliers named by Ofgem as having submitted a Consolidated Segmental Statement under the earlier rules.

The Top Three Suppliers Hold 65% Of The Six Suppliers’ Combined Share

Across the six UK energy suppliers in this ranking, the combined total is 91%. The top three—British Gas, Octopus, and E.ON—hold 65%, equal to 71.4% of the list total. British Gas alone accounts for 29.7% of the list total, while Octopus accounts for 27.5%, leaving the top two close together.

After the 2% gap between British Gas and Octopus, the ranking drops by 12% to E.ON, which is the largest gap between neighbors. The middle of the table is tighter: E.ON leads OVO by 3%, OVO leads EDF by 1%, and EDF leads Scottish Power by 2%. From #1 to #6, the spread is 20%.