Until around 2014, six major companies supplied energy to over 90% of the UK population, known as the 'big six'. Over the years, other smaller companies appeared in the UK's energy market so the 'big six' now refers to the largest companies.

The Office of Gas and Electricity Markets (Ofgem) estimated that, by 2019, the big six held 70% of the market after customers had switched over to smaller energy suppliers (charts now archived).

Who are the big six?

The big six energy suppliers are still the largest companies in the UK's energy sector today. Details on each and their customer numbers are listed below:

British Gas

British Gas is the largest energy company and the greenest supplier of the six. It has now become a branch of Centrica PLC, although in Scotland it is known as Scottish Gas in and in Wales as Nwy Prydain. Its main offices are located in Berkshire. The company supplies gas to 15 million UK households, with 6 million electricity customers.

EDF Energy

This is the British branch of the French company EDF, supplying more than 5.6 million customers. EDF Business Energy has the largest low carbon electricity production with the majority of its supply generated from nuclear sources.


E.ON, formerly Powergen, is well known for business and private power supply, currently serving 5 million customers. The company is renowned for its innovative approach and advanced technology focused on harnessing green energy.


Npower is the smallest of the big six energy suppliers. Outside of domestic supply, it focuses on expanding wind and hydroelectric power. Npower is now a subsidiary of E.ON, although they continue to operate separately. It also cooperates with Sainsbury's Energy.

Scottish Power

Scottish Power is the next largest company above Npower and one of the longest-running provider groups in the UK. It supplies electricity and gas to over 5 million UK households. This is a leading company in renewable energy, after recently closing down its gas and coal plants.


Scottish and Southern Energy (SSE) is the second-largest supplier in the UK and the second-best provider of renewable power. In 2020, it was bought by supplier OVO but continues to operate under the SSE brand. It specialises in hydropower and electric power.

Benefits of choosing one of the largest energy suppliers?

The energy industry has become competitive with new smaller companies supplying energy at low prices. Nevertheless, the big six still have adapted to the drop in gas and electricity prices and continue to dominate the energy market. They have years of experience and they know how to keep their customers happy.

The six largest energy suppliers offer some of the best business energy tariffs for their customers, both in terms of value and additional service extras. They offer a full range of commercial services (from basic fixed prices and flexible 30-day rolling plans to renewable energy solutions) as well as domestic energy services.

Are smaller energy companies worth it?

There has been a rise in small energy suppliers in the UK, some of them offering higher levels of customer satisfaction than the largest energy suppliers. They may also offer cheaper rates for domestic and commercial electricity and gas usage.

The main concern of most people when thinking about switching suppliers to smaller companies is what to do if they go out of business. Ofgem is there to protect consumers in such a scenario. When the electricity providers can no longer serve you, you will then simply be switched to a different company that can. Under no circumstances will you be left without a power supply.

It is always useful to do your research about the different companies that exist in the UK, for example, by checking their online customer reviews. You can find more information about electricity rates here.

Is it difficult to switch energy supplier?

It is common for people to feel reluctant to switch suppliers due to the misconception that the process is time-consuming and complicated. On the contrary, switching energy suppliers is simple and super fast.

All companies deliver their energy in the same way, thus, there is no need to change the pipes and cables of your property if you want to use a different provider. The only difference is the name of the company and the price.

If you wish to switch suppliers, all you need to do is go to Business Energy UK and provide your postcode and power usage. Then, you will be presented with a list of the best available gas and electricity deals. Our online energy comparison tool helps you decide which energy supplier works best for you and makes the switching process straightforward and fast.

Frequently Asked Questions

The prices for gas or electricity supply from the big six energy providers are constantly changing. They come up with competitive deals on a regular basis to serve their customers in the best way. Amongst the cheapest providers are British Gas, SSE and E.ON.

The easiest way to reduce your usage costs is to switch to a cheaper supplier. You can use our online comparison services to compare the prices of all providers in the UK. Simply go to Business Energy UK and add your postcode and your power usage into our comparison tool to receive a list of the best deals available on the market.

In addition to the tariff prices, you can also see the customer satisfaction rates of each supplier and information about how much green energy they use.

If you haven't changed suppliers for a while then maybe it's time to do so. There are lots of great deals on the market you may be missing out on; or even worse, you could be overpaying for your gas and electricity. You can use our supplier comparison tool to find the best deals.

Another reason that may urge you to look for another energy supplier is renewable sources. There are now more options for renewable energy available. If you are environmentally responsible, you may wish to switch to a provider that generated their power from a greener source.

There are a few suppliers that have been certified as using renewable sources, including some of those who are the big six energy suppliers:

  • Green Star Energy
  • Bulb
  • Igloo Energy
  • Shell Energy
  • Octopus Energy
  • Good Energy
  • Economy 7 Energy
  • Tonik Energy
  • Yorkshire Energy
  • Green Energy UK
  • Bristol Energy
  • London Energy
  • Green
  • So Energy
  • Outfox the Market
  • Pure Planet
  • Ecotricity
  • Symbio

An increasing number of suppliers strive to improve their fuel resources and aim at becoming as green as possible. Amongst the biggest suppliers in the market, only Bulb, Octopus and Shell managed to achieve a certification of 100% renewable sources. Other big companies are on their way as well.