UK Energy suppliers: green providers and Big Six

The United Kingdom has a large number of energy providers that supply residential customers with gas and electricity. Below you can find the suppliers we have reviewed so far to help you compare them.

Renewable and clean energy providers

These energy companies aim to source and supply green electricity and in some cases also renewable or carbon offset gas for their customers.

Is your provider charging you too much for a bad product?An independent provide could offer you a green tariff for less. Give us a call today to find out more. Call 020 3608 4293 or Get a free callback now.

More UK energy suppliers

Not all gas and electricity suppliers share the same environmental goals as those mentioned above. There are a great number of energy companies in the UK both, big and small

Big Six

The Big Six is a popular name for the UK energy cartel made up of the six most established companies on the market.

  1. British Gas
  2. EDF Energy
  3. Eon
  4. npower
  5. Scottish Power
  6. SSE

The UK energy market is dominated by six major suppliers who together control 77% and 76% of the electricity and gas markets. Together they are known as the "Big Six" and include household names such as British Gas and E.ON. However, in recent years the Big Six have lost millions of customers thanks to the rise of over 60 smaller independent suppliers.

The Big 6 Suppliers

British Gas

Founded in 1997, British Gas are the UK's largest gas and electricity supplier with around 13 million customers. British Gas supply the highest percentage of renewable energy (43%) of all the Big Six and also had the best customer service record and fewest complaints in 2018.


The second largest supplier with around 7.3 million customers are SSE plc. Founded in 1998, they are based in Scotland but supply gas and electricity to customers across the UK and Ireland. They also rank second in terms of renewable energy supply, with around 21% of their energy sourced from renewables.


E.ON are a global energy company based in Germany. The UK arm of E.ON was set up in 1989, originally named Powergen but were rebranded as E.ON in 2007. E.ON supplies around 7 million customers in the UK and they also own and operate renewable energy infrastructure including wind farms and biomass power stations.


EDF is a subsidiary of its French parent company Électricité de France. EDF launched in the UK in 2002 and has around 5.7 million customers. EDF's energy supply is sourced mostly from nuclear energy (71.2%) and they supply the least amount of renewable energy (11.7%) of all the Big Six.

Scottish Power

The fifth largest energy company in the UK with around 5.2 million customers is Scottish Power. Originally founded in 1990, they were taken over in 2006 by Iberdrola, a Spanish energy company and now serve around 10% of the UK's energy market.


The smallest of the Big Six is Npower which was founded in 2002, originally under the name Innogy plc. They currently supply around 4 million customers. Npower offer the third highest percentage of renewable energy (18.7%) between the Big Six - behind British Gas (43%) and SSE (21%) respectively. Npower also specialises in renewable energy for business.

Big Six Market Shares

British Gas remain the largest electricity and gas supplier, with a 20% share of the retail electricity market and 30% of the gas market. The next biggest energy supplier in the UK is SSE, followed by EON, EDF and Scottish Power. Npower take sixth position with a share of 9% of the electricity market and 8% of the gas market.

Although British Gas remain the UK's biggest supplier, their market share has dropped significantly from 25% in 2013. The rest of the big six have also lost market share over the past five years due to the rise of smaller energy suppliers and the increase in customers switching through comparison services such as Selectra UK.

Electricity Market Share
(April - June 2018)
Gas Market Share
(April - June 2018)
1 British Gas 13m 20% 30%
2 SSE 7.3m 14% 11%
3 E.ON 7m 13% 11%
4 EDF 5.7m 11% 8%
5 Scottish Power 5.2m 10% 8%
6 Npower 4m 9% 8%
  Totals 42.2m 77% 76%

Source: Ofgem.

Big Six Fuel Mix - How much Renewable Energy do they offer?

British Gas offers the largest share of renewable energy in their fuel mix (43%), followed by SSE (21%) and Npower (18.7%) respectively.

Thankfully, all the Big Six suppliers have been increasing their supply of green energy in recent years whilst reducing their usage of coal, with no supplier including more than 10%.

When it comes to nuclear energy, EDF Energy are by far the biggest nuclear energy suppliers with a huge 71.2%. The rest however do not rely on nuclear much, especially SSE who only use 5%.

Natural gas also contributes a major element in the Big Six's fuel mixes, with most suppliers sourcing between 37% and 66% of their energy from natural gas. The exception to this is EDF who only use 9.4%.

Overall then, unlike many green suppliers who offer 100% renewable energy, the Big Six still have a way to go to be as green as their smaller rivals. But if you're keen on choosing one of the Big Six AND going green, British Gas are your best bet!

  British Gas EDF Energy E.ON Npower Scottish Power SSE
Renewable 43% 11.7% 16.7% 18.7% 15% 21%
Coal 7% 7.6% 10.1% 9.8% 7% 7%
Natural gas 37% 9.4% 53.5% 52.3% 66% 65%
Nuclear 11% 71.2% 16.2% 15.9% 10% 5%
Other 2% 0.2% 3.5% 3.3% 2% 2%


The Big Six's Electricity and Gas Prices in 2018

Big Six Electricity and Gas Prices 2018

To compare the prices of the Big Six, we gathered quotes from each of their standard variable tariffs. Using the UK's average household usage figures - 3,100kWh of electricity and 12,500kWh of gas per year, we used the same London postcode to compare prices as closely as possible.

As you can see below, the Big Six actually charge similar rates for gas and electricity on their standard tariffs. EDF Energy appears to be the most expensive supplier among the Big Six at around £1,305 per year for the average 2 bed house in London. British Gas offered the cheapest quote at £1,120, a difference of £185 per year.

Supplier Avg. per year (Elec.) Avg. per year (Gas) Total per year
British Gas £543 £577 £1,120
EDF Energy £669 £636 £1,305
E.ON £592 £612 £1,204
Npower £626 £627 £1,253
Scottish Power £629 £607 £1,236
SSE £595 £611 £1,206

Quotes gathered in July 2018. Source: Energy supplier websites.

The Big Six's Customer Service

With such huge numbers of customers, ensuring a consistently high standard of customer service is not easy for any supplier. Many customers stick with the Big Six names due to their familiarity and well-known brand name, but does this mean customers are actually satisfied with their customer service?

Looking at the Ofgem's research below, it's clear that none of the Big Six excel when it comes to customer care. Npower and Scottish Power customers appear to be the least happy with their supplier's service, bills and contacting the customer service team.

SSE on the other hand lead the big six in all three categories and have the highest percentage (35%) of customers that would recommend their supplier. Whilst they may offer the best service of the Big Six, only one in three customers would be happy to recommend SSE which is pretty poor overall.

  British Gas EDF Energy E.ON Npower Scottish Power SSE
Customers satisfied with service 71% 68% 71% 65% 68% 74%
Customers satisfied with understandable bills 73% 71% 74% 70% 70% 73%
Customers satisfied with contacting supplier 75% 68% 70% 65% 65% 75%
Customers that would recommend their supplier 35% 29% 33% 28% 28% 35%

Correct as of February 2018. Source: Ofgem.

Big Six Complaints

Between the Big Six, Scottish Power receive the most complants with around 2,800 complaints for every 100,000 customers. However, SSE and E.ON follow closely behind, both with around 2,500 complaints each per 100,000 customers. Interestingly, British Gas can boast the fewest complaints with just under 1,500 per 100,000 customers.

Npower is the supplier that takes the longest to resolve complaints - only solving aound half of customer complaints within one working day. Compare this to E.ON who manage to resolve a much better rate of 78% of complaints within a day.

  British Gas EDF Energy E.ON Npower Scottish Power SSE
Complaints per 100,000 accounts * 1,486 2,291 2,517 2,208 2,799 2,546
Complaints resolved within 1 day * 60% 58% 78% 49% 54% 77%

* Third quarter 2018 (July - September). Source: Ofgem.

Other UK energy utility companies

The United Kingdom has a massive amount of smaller companies trying to get a slice of the retail energy pie. Here's just a few of them:

  1. Sainsburys Energy
  2. Southern Electric(now part of SSE)
  3. Spark Energy(shut down by Ofgem)
  4. Atlantic (now part of SSE)
  5. SWALEC(now part of SSE)
  6. Utilita
  7. Utility Warehouse
  8. Zog Energy

What do UK energy companies do?

The UK energy sector is made up of several layers:

  1. Energy generators generate electricity both in renewable and non-renewable ways.
  2. The National Grid links up the energy producers through a high capacity network designed to carry electricity from one end of the country to the other.
  3. Distribution Network Operators are responsible for stepping down the high voltages from the national grid so they are suitable for residential use locally.
  4. Finally, energy providers bill you for the energy you use in your home.

Energy suppliers are the last step in the energy journey, their one job is to charge you for the energy you use. They buy up gas and electricity in bulk on a wholesale market so they can then sell it on to British households and businesses for profit.

This energy wholesale market is similar to a stock market with the price of electricity and gas fluctuating depending on demand and supply. Energy providers try to buy energy at low prices when electricity generators are outstripping demand on the national grid. This allows energy providers to sell it on to their customers with a sizeable markup that goes straight to their bottom line.

The opposite can also happen where demand comes close to meeting the outer envelope of supply which then drives up energy prices on the wholesale market. In those situations, energy companies may make less money or even lose a little.

While British energy companies play the energy wholesale market, regular customers are insulated from sudden changes in energy prices through two main types of tariffs which most energy suppliers adhere to:

  • Variable-rate tariffs have energy unit rates that can change from one month to the next. These changes are usually driven by the seasons with unit rates increasing in winter and falling in the summer.
  • Fixed-rate tariffs have rates that are set in stone for a fixed period of time, usually a year. While a household’s energy bill might change because of variations in energy use, the underlying rates will not during the duration of the tariff.

While it might be tempting to think that one energy company will provide better quality gas or electricity than another, that’s simply untrue. Every UK household gets the same kind of gas and electricity through the national grid and their local Distribution Network Operator, no matter where they are.

Going with a cheaper energy provider doesn’t mean more power cuts or brownouts. In fact, in the unfortunate event of a power outage, your energy supplier will only be able to refer you to your Distribution Network Operator or a national power outage helpline who will actually be responsible for dispatching engineers who can fix the problem

Telling them all apart

The main differences between energy companies for UK customers are as follows:

  1. Customer service quality varies from one energy utility to the next. This can impact how quickly and effectively billing issues or queries are resolved. Long call wait times and unclear communication are symptoms of unsatisfactory customer service which can erode customer trust in a company.
  2. Pricing is the other main area which varies across providers and, in some cases, even within the very same provider. Different providers will offer different rates within their tariffs and energy advice services, such as Selectra, let you compare them like for like.
  3. Energy sourcing varies from one energy supplier to another due to different wholesale purchasing practices. Some companies will make it a priority to buy green electricity while others will go with electricity coming from nuclear or coal power stations without giving it a second thought.

Green energy companies are no longer more expensive than companies that are less caring when it comes to the environment. Renewable electricity is competitive when stacked against less environmentally-friendly sources. Using greener electricity comes down to mere willingness to do so in this day and age.

Voting with your wallet

Since a more expensive provider doesn’t net UK energy consumers a more reliable gas and electricity supply, there is no point staying with a company that overcharges its customers. The UK energy market privatisation was justified as a way of giving all Britons more choice and better prices for their gas and electricity.

This means that UK households are responsible for finding the best deal for their home. However, over 70% of people stick with the same big energy company instead of shopping around for a leaner and more competitive supplier.

It’s worth noting that the majority of the big energy suppliers listed above are owned by foreign companies. Anyone staying with these suppliers out of a sense of patriotism is misplacing their loyalty. Take Scottish Power, for example, they are owned by Spanish energy giant Iberdrola.

How to pick a winner

With so many energy companies doing essentially the same thing, picking the right one for your home is no easy feat. Here at theSwitch, we have a few pointers to get you started:

  1. When comparing energy tariffs make sure you find the unit rate and standing charge amounts for each one to get a clear idea of which one offers better value for money.
  2. Do a little research on the company to get a better idea of the type and quality of service they offer. By clicking on the company names above, you can read our in-depth guides. You can find out everything from customer opinions to the supplier energy mix.
  3. If you’ve just moved into a new home or don’t know how much energy you use every year, use an energy estimator to better understand your gas and electricity consumption.
  4. Speak with an energy advisor to get an idea of what company has the best prices for your area. Alternatively, if you don’t fancy talking on the phone you can also do an online comparison.
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