Who are the biggest energy suppliers in the UK?

Energy in the UK is supplied from a number of sources and by around sixty suppliers. Taking into account the whole of the UK energy market, here is an up-to-date breakdown of those sources:

  1. Gas: 39.4%
  2. Renewable Sources: 37.9%
  3. Nuclear: 16.6%
  4. Coal: 3.9%
  5. All others: 2.2%


With this variety of possible sources comes a variety of companies to supply that energy to your home or business. The traditional ‘big six’ energy suppliers lead the way with over 70% of the market share. Between them they supply 7 of every 10 households throughout the UK.

Big Six breakdown

  1. British Gas. The UK’s longest established energy firm is now the biggest provider of green energy. For electrical generation British Gas uses 24% Nuclear Power and 76% Renewables. This means that the suppliers 11 million+ customers are producing 0g CO2 when it comes to being supplied electricity.
  2. Scottish Power. Combining all tariffs offered by Scottish Power shows that they supply 50% of energy from gas, 36% renewable, 6% nuclear, 4% coal and 4% renewables.
  3. EDF. This is the UK’s biggest supplier of nuclear power which shows in the breakdown of energy sources. 66.6% is from nuclear, 20.5% renewable, 9.3% gas, 3.5% coal and 0.1% other.
  4. E.ON. This company is driving hard towards renewable sources. This is reflected in a UK average of 46.3% of energy sourced from renewable sources. 42.2% comes from gas, 4.8% nuclear, 3.7% coal and 3% other.
  5. SSE. This supplier uses 52% renewable sources and 48% natural gas.
  6. Npower. 54.4% gas, 30.7% renewable, 6.2% nuclear, 4.8% coal, 3.9% other.

British Gas is by far the biggest energy supplier with over 11 million customers. Ever since energy supply ended its time as a state-run commodity, British Gas has been the frontrunner of this market. Despite growing competition in the UK energy market, this position at the top is unlikely to change any time soon.

Next is OVO/ SSE with 9 million customers. OVO does not get credit amongst the ‘big six’ but has muscled its way to the top end of the industry. Having bought SSE in 2019, OVO brought in an extra 5 million customers under its umbrella. 

EON is third on the list and supplies around 7 million customers in the UK.

With 6 million customers EDF finds itself fourth on this list of biggest suppliers. This French owned company acquired British Power back in 2009 to make it the biggest supplier of nuclear power.

In fifth and sixth places are Npower and Scottish Power with around 5 million customers each. As well as placing highly on this list, Scottish Power also owns a large part of the energy distribution network in Scotland and the North of England. In 2006 it was bought by Spanish firm Iberdrola who then became the third biggest energy supplier in Europe.

Market Share

Big Six

  1. British Gas: 18.23%
  2. OVO: 15.34%
  3. E.ON: 12.04%
  4. EDF: 10.73%
  5. Scottish Power: 9.11%
  6. Npower: 6.53%

Medium Sized Suppliers

  1. Bulb: 5.74%
  2. Octopus Energy: 5.14%
  3. Shell Energy: 2.69%
  4. Utilita: 2.61%
  5. Utility Warehouse: 1.88%
  6. Avro Energy: 1.64%
  7. Green Network Energy: 1.35%

Energy suppliers that are considered to be small make-up 6.96% of the market share.

How have things changed?

Between 2011 and now the market share for the big six has fallen from almost 100% to 72%. While this still accounts for a very large portion of the market, it is clear to see that conditions are changing. OVO’s buy-out of SSE has had a major effect on these figures as although they are now the second biggest supplier, they are not considered one of the traditional big six.

The 6.96% market share which is held by various small-scale suppliers also out-paces Npower’s 6.53%. This shows that although the market is far from perfect, competition is working. Not only can customers now compare the tariffs of each company easily through comparison websites, they can also choose a supplier based on values. For example, a number of green energy companies are starting to bite into that market share based on pledges to only use renewable sources. This has led to the bigger companies lending resources towards their own fuel mixes in order to keep step with innovation.

With regards to energy supply, the change has been nothing short of staggering. Coal, once a dominant source of the UK’s power is now among the lowest. Wind power was unheard of in the early 1990’s and yet now makes up the majority of our renewable energy. These huge infrastructure changes are down to public perceptions and are proof that markets primarily rely on consumers and not the other way around. When enough customers demand change, they will get it. This is why competition helps keep the energy market healthy and makes sure headlines of ‘price fixing’ and ‘bullying tactics’ are resigned to the past.


Hi, I'm Rob and I run I initially started this project 5 years ago when I was looking to switch energy suppliers and found there wasn't a website that provided simple, data backed reviews on all the suppliers available. Since then, I spent have a lot of time (too much some may say!) looking at all publicly available data about each supplier and writing reviews using this information. These reviews are updated as regularly as possible and any data is backed up by a source where necessary. I have also started writing guides on various energy related topics which hopefully you will find useful. If you find any issues, please use our contact form to let us know.

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