Who are the big six energy suppliers?

If you’re looking for energy or preparing for a future energy switch, then you’re sure to have seen the same major names recurring during your search. Most of these big-hitters of energy are household names, and go-to energy suppliers for anyone looking to secure an energy plan. So, before you go ahead and pick a massive name to supply your energy for the future, consider if these brands really are the fail-safe choice for reliability and if they can live up to their reputation.

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Last updated: 11 March 2021

In this guide you’ll find:

  • Who are the big six energy companies? 

  • What's the big six energy suppliers' market share?

  • Why do we have a ‘big six’ group of energy companies?

  • How do small energy suppliers differ from the big six?

Who are the big six energy companies?

As of 2021, the list of UK energy suppliers that fall under the ‘big six energy’ umbrella are:

British Gas

Perhaps the leading household name in terms of UK energy suppliers, British Gas has a history that dates back to the 1800s. It offers all the services you’d expect from one of the top energy companies, such as supplying gas and electricity, and some you might not, like boiler insurance and landlord cover. 


Offering home and business energy plans, as well as 100% green electricity and solar panel installation, E.ON appears near the top of any search engine list of energy suppliers. It was established in Germany in 2000 and has grown to become one of the top energy companies in the UK.


Founded in 1998 and based in Perth, Scottish and Southern Energy, commonly known as SSE, was one of the UK’s most popular energy companies that also branched out to offer extra services such as insurance and broadband deals. In 2019, SSE agreed that OVO Energy would acquire its customer base. There was uncertainty for a while about whether OVO would replace SSE as one of the big six energy suppliers or if both brands would continue to be present in the market, making a big seven. However, in 2020, the national regulator Ofgem began tracking the performance of the integrating companies under the name OVO Energy, so expect that brand to come increasingly to the fore as 2021 progresses.


npower was formed in 2000 and is based in Swindon. This big six energy company offers plans that use 100% renewable electricity and business energy plans.

EDF Energy

EDF is a French company based in London that was founded in 2002. As well as a range of energy plans, EDF offers boiler services, electric car leasing and feed-in tariffs for customers who generate their own renewable energy. 


ScottishPower was established in 1990 and is based in Glasgow. It offers 100% green electricity on its fixed-priced energy plans. It also has charitable plans that support Cancer Research UK.

Other UK energy companies

If you’re making a list of energy suppliers in preparation for a future energy switch, then you’re bound to have seen the same big six names popping up when searching for UK energy companies. Most of these will be household names and you might presume that they are the top energy suppliers for anyone looking to secure the best energy deal. But there are alternatives to the big six energy companies, so before you plump for one of the well-known brands, you should consider whether these companies provide a fail-safe choice for reliability and whether they can live up to their claims.

What's the big six energy suppliers' market share?

The big six are named as such because they are the leading suppliers of energy in the UK. Combined, the big six supply about 70% of the UK’s household energy, but it’s worth noting that this has significantly decreased since the early 2000s when the big six energy companies supplied almost 95% of UK homes.  

This table shows how much of the domestic electricity market the big six energy suppliers have enjoyed over the last three years and the erosion caused by smaller UK energy companies. 

Q1 2018Q1 2019Q1 2020Q3 2021
British Gas20.3% 18.9% 18.4%18%
EDF 11.2% 10.8% 10.6%10.4%
E.ON 13.5% 12.5% 12.1%12.3%
npower 9.3% 8% 6.7%5.8%
ScottishPower 10% 9.8% 9.2%8.9%
SSE 13.9% 12.8% 0%0%
Shell Energy 2.8% 2.5% 2.9%2.9%
OVO 3% 4.5% 15.8%14.9%
Utilita 2.1% 2.5% 2.6%2.7%
Utility Warehouse 1.8% 1.9% 1.9%1.9%
Bulb 1.1% 3.7% 5.7%5.9%
Octopus 2.1% 4.9%5.7%
AVRO 1.4%1.9%
Green Network Energy 1.2%1.3%
Assorted small energy suppliers 10.9% 10.2% 6.7%7.7%

Data supplied by Ofgem, January 2021.

Why do we have a ‘big six’ group of energy companies?

Being on the big six list of energy suppliers doesn’t award companies any privileges, though their larger customer bases often mean they can offer a wider range of services. However, there has been a real push by smaller UK energy companies to disrupt the industry in recent years. Successive UK governments have encouraged competitiveness between energy suppliers since 2010, which has reined in the influence wielded by the big six energy companies. Ofgem has also supported this by introducing UK energy price caps. So, while choosing one of the big six energy companies as your supplier minimises the risk of your provider suddenly falling into administration as these energy companies each have a large customer base, you don’t necessarily gain anything from their plans that smaller suppliers outside the big six can’t match.

How do small energy suppliers differ from the big six?

If you study a more comprehensive list of energy suppliers, you’ll see how small energy companies in the UK are cutting themselves a niche in the market by offering things that the big six energy companies may not be able to match. For example, while the big six are making efforts to offer green energy, some smaller suppliers can embrace this ethos more fully, such as Bulb Energy, which is also able to offer a simple, single tariff and champion a warm, friendly and notably less corporate approach towards a customer base keen to reduce its carbon footprint.

Other things that give small energy companies the edge include customer service. Larger big six energy suppliers may have turned to non-UK call centres or simply have lost the ‘human’ touch that often occurs with any larger-scale business. In contrast, energy suppliers like Octopus Energy have expanded their customer service approaches so that as well as traditional phone lines, they have email, instant messaging and social media communication channels that help it to quickly resolve any customer issues. 

Small energy suppliers and ethical approaches 

Further, there are small energy companies in the UK who align their approaches closely with an ethical standpoint, such as Ebico Energy, which styles itself as an energy company looking to combat fuel poverty in the UK. Its not-for-profit business model allows it to concentrate on keeping costs down for the customer and it also has its own charity.

This isn’t to say that smaller companies are inherently better than those included in the big six group of energy suppliers, but it is worth researching and comparing energy deals from an array of energy companies. UK suppliers offer a diverse range of plans, so you should be able to find the perfect match for your needs.

Frequently Asked Questions

How is electricity supplied in the UK?

The largest of the big six energy companies is British Gas, which supplied around 5.36 million homes with electricity in 2019, and 6.59 million with gas. 

In terms of electricity generation, less than half of the power generated by UK energy companies now comes from fossil fuels – it was down to 43% in 2019 according to the climate and energy website Carbon Brief. Low-carbon sources provided 54% of electrical output, with 37% of that coming from renewables, such as wind and solar power. As part of the Climate Change Act, the UK has pledged to produce net-zero greenhouse gas emissions by 2050, which means that the big six and their smaller rivals will need to rapidly shift towards producing even more low-carbon energy in the coming decades.

Who will be the big six energy companies in the future?

The big six has seen an unprecedented shake-up in the past few years as more and more small suppliers move into the market. While there is always a risk that some of these smaller energy companies could go bust, other fledgeling UK energy suppliers have experienced significant growth and are well on their way to being a strong threat to the UK’s big six energy suppliers.

Bulb, for example, has seen a recent market share increase to 5.9% for domestic electricity, and while that may not seem like much of a threat to British Gas’s 18% share, it makes it a serious competitor to other members of the big six. Indeed, if current trends continue, there is the chance that smaller energy companies will win over enough customers to cut the big six down to the big five, or even reduce their market share so significantly that today’s top energy companies have no more power over the market than their tightly focused rivals.