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A Guide to Britain's 'Big Six' Energy Suppliers

electricity switches

The Big 6 are an unofficial grouping of the UK’s biggest suppliers of electricity and gas. While they still hold an undeniable majority in the UK energy market, their percentage of the market has decreased substantially. In the last five years smaller, newer competitors, like Tonik and Octopus Energy, with cheaper prices and stronger customer service have been able to take more and more of the energy market from the famed Big 6.

Who are the Big Six?

Let's find out more about these giants of UK energy supply controlling most Britons' gas and electricity.

British Gas

British Gas

The largest of the Big Six companies, British Gas, has their roots in the Gas Light & Coke Company, the very first public utilities company in the world. Since then they have been nationalised, then privatised again to eventually form British Gas plc. in 1986.

They began supplying electricity two years later. Decades of marketing, including the famous Tell Sid campaign, has made British Gas a household name within the UK.

British Gas is the biggest energy supplier in the UK. As of Q3 2018, they held 19% of the UK energy market. They supply energy to more than 11 million homes.

British Gas guidesFind our more about their tariff pricing, how they fare in terms of customer service as well as how to contact the right department.



SSE (also known as Scottish and Southern Energy) was founded in 1998 from the public sector authorities that previously administered regional energy supply: the North of Scotland Hydro-Electric Board and the Southern Electricity Board. They are the largest producer of renewable energy in the UK. In Q3 2018 they had a 13% market share.

In recent years there was a rumored merger between SSE and npower, but it was ultimately scrapped in late 2018.

SSE in-depth guidesMore information about their tariffs and pricing, how they are rated in terms of customer service as well as the best way to reach SSE directly.



E.ON is the largest investor-owned gas and electricity company in the world. It formed with the merger of two German energy companies, VEBA and VIAG, and began serving British customers after acquiring Powergen.

E.ON has invested largely in social media and renewable energy projects. As of Q3 2018 they held 13% of the UK market share.

E.ON's big six status has been in flux recently with the news E.ON and Npower merger, which could rock the Big Six power balance.

E.ON informationGet in depth analysis of their tariffs, offers and pricing, what the reviews say in terms of customer service as well as how to get in touch.



npower began as part of National Power in 1990. Over a series of separations, mergers and acquisitions, it eventually became the German-owned npower we know today.

The company has a large involvement in the charity sector and a partnership with the Macmillan cancer support trust. As of Q3 2018, they held a 9% market share in the UK. In 2019, npower has merged with E.ON, which, has led to significant job cuts in an attempt to mitigate losses.

npower detailed guidesSelectra has researched npower tariffs, reviews and customer service track-record as well as the best ways to contact this supplier.

EDF Energy


EDF Energy is owned by the French Electricité de France, who entered the UK market in 1998. EDF was the French national supplier until the relatively recent deregulation of the energy market across the channel.

EDF is both the largest supplier by volume of electricity and the largest producer overall of low-carbon electricity in the UK. They’ve made efforts to engage their local communities with eco-friendly events. In Q3 2018 they supplied 8% of the UK market.

EDF energy reviews and detailsSelectra gives you everything you need to know about EDF tariffs and plans, reviews and ratings based on customer service and the easiest ways to contact them for all your queries.

Scottish Power

scottish power

Scottish Power is now part of the Iberdrola S.A. Group, based in Bilbao, Spain. Just like SSE, Scottish Power traces their roots to earlier regional energy boards. They’re the UK’s largest generator of wind energy and are investing further in renewable energy.

Scottish Power detailsGet accurate information about their own tariffs, reviews of their customer service and account management as well as the fastest ways to get help from Scottish Power for all your queries.

Big 6 market share

The combined market share of the Big 6 remains impressive. According to Ofgem, in Q3 of 2018 they held around 75% of the UK energy market.

Even more impressive is how much of the market they’ve already lost. As recently as 2009, the Big 6 held a full 100% of the market. Much of that loss has happened in the last five years, leading many people in the industry to believe the Big 6 will need to change their tactics to avoid further decline.

How They Conquered the Market

The UK energy sector has a long history of private companies being nationalised, then re-privatised, and merged with foreign companies. This history has given the Big Six a market advantage, which many critics claim is unfair and harms the consumer.

The Big Six are the companies that were able to absorb what had previously been the national gas and electricity boards, which had been state-run regional monopolies. This gave them a huge head start.

Some of the Big Six companies, particularly British Gas, enjoy a long history and strong name recognition in the UK.

As many people find the idea of switching suppliers a daunting one, they’re hesitant to make the switch to a different supplier, even if they could save money in the process. However, this is largely due to large swathes of the British public being misinformed or apathetic with regards to energy.

There are lots of myths about the difficulty of switching energy suppliers: you could lose your energy supply, some suppliers have a less reliable supply of energy, etc. But ultimately, none of those things are true. Switching energy suppliers can be a quick and painless way to save money every month!

Company profits

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While the revenues of Big 6 companies are still much higher than their competitors, their profit margins have begun to decrease over the last few years.

As more customers switched suppliers to get a better deal, recently annual profits fell by 10% to a still whopping £900 million.

More competitive suppliers and more public awareness of different tariff rates have caused many households to switch energy suppliers. This is slowly but surely cutting into the Big 6’s majority of the UK market, which of course has also cut into their profits.

Who owns the Big Six?

It’s worth knowing who ultimately owns the energy suppliers, especially if you’re interested in investing in shares. For example, if you’re interested in buying Scottish Power shares, you’d actually buy shares in Iberdrola, a Spanish multinational.

Although the Big Six are ubiquitous names in the UK energy market, most of them are owned by large foreign multinational energy companies. Only British Gas and SSE are part of British owned companies.

British gas ownership

British Gas is owned by the British Centrica plc, a multinational energy supply company that supplies the UK, Ireland and North America. They’re also the owners of Scottish Gas and Bord Gáis Energy and have recently taken over the Danish company Neas Energy (now named Centrica Energy). Centrica is listed on the London Stock Exchange as CNA.

SSE ownership

SSE (formerly known as Scottish and Southern Energy) does not have a parent company, and is itself the owner of SWALEC, Atlantic and Airtricity, Scottish Hydro, and Southern Electric. It is a Scottish company and trades on the LSE under the name SSE.

Eon details

E.ON (or e·on in their marketing materials) is a holding company based in Essen, Germany. It’s one of the world’s largest investor-owned electric utility companies and supplies energy in over 30 countries. It’s traded on the Frankfurt Stock Exchange as EOAN.

npower owners

npower is currently owned by RWE, a German energy services company. The RWE is traded in the Frankfurt Stock Exchange as RWE. After the failed merger with SSE, npower leadership has stated they now plan to merge npower under E.ON, with possible layoffs.

edf energy owners

EDF is owned by Électricité de France, a formerly state-owned electricity supply company in France. EDF entered the UK market with the purchases of SEEBOARD Plc, London Electricity Plc, SWEB Energy Plc, coal and gas power stations and a controlling share in British Energy.

edf energy owners

Scottish Power is owned by the Spanish multinational company Iberdrola. Iberdrola operates in dozens of companies and, in addition to Scottish Power, owns the US energy supplier Avangrid and the Brazilian supplier Elektro Holding. Iberdrola is traded in the Bolsa de Madrid (Spain’s largest stock exchange) as IBE.

Concerns & problems with Big 6 Companies

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Until very recently, virtually all UK households were supplied by one of the Big 6 energy companies. This gave the firms little incentive to lower their prices as in the past up-and-coming brands were too small to make a difference.

There have even been accusations that the Big 6 have colluded. (Collusion is when brands agree, tacitly or explicitly, to keep prices high to maintain higher profits.) But all inquiries have found that their actions were completely legal.

Big 6 companies have also been accused of having deliberately confusing tariff rates and policies, and automatically defaulting customers onto more expensive variable tariff plans. The fact is that some Big Six companies have taken advantage of the British public through confusing pricing and billing practices. With customers finally starting to shop around for more competitive pricing, the Big Six are starting to put resources into improved customer service.

Energy pricing

The biggest mark against the Big Six is their historically high prices. All of the six companies have generally maintained prices significantly higher than their smaller competitors.

More recently, with market share sliding towards newer and more agile energy companies, large gas and electricity providers like EDF and British Gas have begun to create exclusive tariffs for energy comparison services in order to recapture customers with surprisingly good pricing. That's why it's always worth comparing online or over the phone while having a solid understanding of how much you use in your home.

Reviews: Where do the Big Six stand?

Apart from their higher prices, the Big 6 also suffer from low customer satisfaction. Across the board, customers have generally complained of poor customer service, billing issues and problems with their apps and online service. npower in particular has an underwhelming 92% bad rating on Trustpilot.

20 minutes just to get through [...] punted to the 'move in department' [...] no resolve for a simple thing.
Bryn with npower

The one partial exception is EDF, which has a respectable rating and some positive notes on their customer service.

I've found EDF to be helpful [...] their overall performance and contact centre staff are [...] good.
Darren with EDF

Newer Independent Energy Suppliers

There are now over 60 different suppliers of gas and electricity in the UK. Many of the newer arrivals sport lower tariffs and higher rated customer service than the Big Six companies.

Some of the best ranked companies in terms of customer service and value for money are Tonik Energy, Octopus Energy, and Ovo Energy.

Interested in green energy? Companies including Tonik Energy and Bulb guarantee REGO-backed, 100% renewable energy produced electricity tariffs and 5-10% renewable gas tariffs.

If you’re looking for more info on the UK’s smaller energy suppliers, we’ve broken them down in our small suppliers guide.

Why switch providers?

As more and more new energy providers enter the market, consumers are reacting more strongly to higher energy bills. More households are switching away from the Big Six energy companies than ever.

If you’re currently with one of the Big Six Energy companies, there’s a very simple reason to switch: you could be paying less every month, while receiving better service!

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