Who are the big six energy suppliers?

Who are the big six? And what other energy suppliers are there? Let’s take a look.

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For a while, a group of six companies - known as the big six - dominated the energy market.

But with energy becoming more affordable, the energy market has become competitive. The big six have had to make way for smaller energy companies.

In the last 10 years, the market share of large companies like the big six dropped from 100% to 70%. With smaller energy companies making up 30%.

But who are the big six? And how do they compare to the smaller energy companies?

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Who are the big six energy companies?

Now that the market has become more competitive, the big six have been renamed by Ofgem as “large legacy providers”.

The rest of the companies on the market are known as other large, medium and small suppliers.

The big six, or the large legacy providers are:


British Gas

Now owned by Centrica, British Gas has been providing energy to homes for 200 years.

As of 2020, they had 6.9 million energy customers.



EDF stands for Electricité de France and it’s owned by the French Government.

There were around 200 energy companies in France in the 1930s.

The price you paid for energy then depended on what part of France you lived in. So, the government decided to form one company now known as EDF.

EDF came to Europe in 2000, and as of 2020 had 4.8 million customers.

In the UK, EDF plans to invest in low carbon technologies. Amounting to 12GW of wind, solar and nuclear power and meeting one fifth of the UK demand.



Formerly Powergen, E.ON formed when VIAG AG and VEBA AG merged in 2000.

Prior to the merger, these companies were founded in the 1920s.

E.ON’s electricity is matched by renewable sources like wind, biomass or solar. And since 2009, E.ON has invested more than £3.3 billion in wind, solar power and biomass. As well as other renewable energy sources.



Southern and Scottish Energy - or SSE - has 3.6 million electricity customers, and 2.4 million gas customers

They formed after Scottish Hydro Electric Transmission and Southern Electric merged.

In January 2020, SSE became part of OVO energy.



With roughly 6.5 million customers, Npower has one of the biggest customer bases in the big six.

In 2019, they were bought out by E.ON.

All Npower customers will be moved over to E.ON next, which is a subsidiary company of E.ON.


Scottish Power

Scottish Power has recently merged with Yorkshire Energy, and has around 5 million customers.

They’re part of the Iberdrola group, and only generate energy through renewables like wind and solar, to name a few. 


Why are there so many energy supplier choices?

Energy was privatised in 1990, meaning it’s now owned by businesses rather than the government.

So technically, anyone could start an energy company.

According to Ofgem, wholesale energy prices have been steady since 2010.

This combined with more businesses being able to work solely online could be the reason why so many energy companies have started up.


What other energy suppliers are there?

As we mentioned, Ofgem categorises energy companies other than the big six as other large, medium and small. Where they land in these categories depends on the company’s market share.

For other large companies, Ofgem looks at market share of the company before energy was privatised, and its current market share.

Other large companies have market share of at least 5% after increasing their market share from below 5% when energy was privatised.

Some examples of other large energy companies are:

  • OVO
  • Octopus 

Medium suppliers have a market share of over 1%, but below 5%. Some examples are:

  • Shell Energy
  • Utilita
  • Avro Energy 

Small suppliers have a market share of below 1%. Some examples are:

  • Co-operative Energy
  • Ebico
  • Daligas

You can find more information on Ofgem's website.


Which energy supplier should I pick and why?

There’s a lot of choice in the energy market. In fact, as of 2020, there are 52 energy suppliers on the market. 

So how do you decide on an energy company? According to Ofgem, how energy is produced and supplied, its affordability, and its environmental impact are the main issues on the public’s mind.

Some companies offer sustainable energy options, for example wind and solar power.

Customer service is another important factor. If you need to discuss your energy tariff, you want to know you can resolve issues with your supplier easily.

Ofgem says that customer satisfaction is at an all-time low. The biggest drop in satisfaction was with large suppliers in 2021, dropping by four percentage points to 69%. Small suppliers remained consistent though, holding their customer satisfaction level at 70%. 

Although the choice is there, smaller energy companies are more likely to go bust than the big six energy companies.

For example, 26 energy companies were taken over in 2020, according to Citizens Advice. Most of these were taken over by one of the big six energy companies. 

You could find that sticking with a big six company means more stability. As they’re less likely to go bust.

But it’s worth shopping around as the market is unpredictable. A small energy provider could one day grow to become stiff competition for the big six.

If your energy provider does go bust, Ofgem will usually move you to an alternative energy supplier automatically. If you’re not happy with your new provider, you can always switch.

Households and businesses spend around £55 billion on energy each year. So if you’re price orientated, you can shop around for energy using sites like ours. 


What does the future of the big six look like?

With smaller and medium energy companies making gains, it could be that the energy market becomes more of a level playing field in the future.  

But the might of the big six makes them relatively stable. Their existing expertise means they’re extremely experienced, while there’s always a risk that smaller companies could go bust

That said, medium energy companies in the UK have experienced growth over the past few years. And in March 2021, 37% switched away from large energy suppliers. Up from 31% in February 2021.

Newer suppliers are becoming more tech savvy too, meaning they’re able to offer top level customer service. Something that companies like the big six may not be able to provide.