Skip navigation

The big 6: a guide to the UK’s top energy providers


We explain who the big six UK energy suppliers are, what they do, green energy and switching suppliers.

light bulb

You’ve heard their names, seen the TV adverts, and quite possibly paid them money for your gas and electricity, but what else do you know about Britain’s ‘Big 6’ energy providers.

The Big Six

There are around 20 different gas and electricity suppliers in Britain. They all offer a range of tariffs, from cheap deals to ones that help you go green, but it’s fair to say that six of them in particular dominate the energy market.

British Gas

British Gas is the leading energy provider in the UK, supplying over 11,000,000 homes with gas and over six million homes with electricity.

The company is part of Centrica plc; a UK quoted FTSE 100 energy company, and is also involved in related energy activities across the United States, Canada and some parts of Europe.

British Gas intends to provide the best value energy in the country, and has stated a commitment to providing renewable, sustainable energy through micro-generation technology initiatives such as cell-powered household boilers.

In fact, the company claim its electricity has the lowest CO2 emissions of all the major UK energy suppliers.

EDF Energy

EDF Energy is the largest supplier of electricity to London, the South East and South West of England.

The company manages coal and gas-fired power stations, private CHP (combined heat and power) plants and wind farms, and owns and operates an energy infrastructure which distributes power to a quarter of the population.

EDF Energy supports initiatives to fight climate change through new technology, and through school visits and the implementation of a specially-designed website, EDF educates children on how to be safe around electricity.

Note: Union Energy, though not actually a supplier, trades off EDF’s licence, so in effect is affiliated to the Big 6.

Union Energy specialises in providing low-cost domestic gas and electricity to trade Union members and their families. The company is endorsed by over 50 trade unions and works in partnership with ScottishPower, one of the largest UK energy suppliers.


E.ON provides gas and electricity for around 9,000,000 homes in the UK, and is the world’s largest investor-owned energy company. As well as providing energy, the company also own and operate their own power stations and run the East Midlands electricity distribution network.

E.ON owns and operates 20 wind farm schemes across Britain. They also source green energy from a variety of hydropower schemes, including Rheidol, the largest hydro power station in England and Wales. E.ON is aiming to increase output from renewable sources to 1,100MW by 2010.

gas hob


npower supplies electricity, gas and related energy services to nearly 7,000,000 customers and also generates its own electricity. As well as operating and managing low-cost coal, oil and gas-fired power stations, the company generates renewable energy through hydro and wind power, and are developing innovative energy-related technologies.

With around 8,500 staff, npower is one of the UK’s largest energy providers. Launched in 2000, the company was formerly a collection of seven smaller gas and electricity supply businesses. 

npower hopes to commit business with a sense of responsibility, and are an active member of the 'Percent Club', in which they invest more than 1% of their pre-tax profits back into the community.


ScottishPower are one of the longest-running UK energy groups, serving over 5,000,000 gas and electricity customers in the UK and employing around 24,000 staff worldwide. The company maintains four distinct areas of business, in which they:

  • supply gas and electricity to UK customers

  • implement a diverse generation portfolio, including the operation of the UK’s leading wind farm operator

  • own and operate an electricity and distribution network

  • are a major wind farm developer

When it comes to green energy, ScottishPower were the first energy company to be approved by the Scottish Government for a planning grant, allowing them to create the £200 million Harestanes wind farm in Dumfries and Galloway. The project provides enough green energy to power up to 120,000 households.

Note: Sainsbury’s Energy, though not actually a supplier, trades off Scottish Power’s licence, so in effect is affiliated to the Big 6.

Sainsbury’s, in partnership with EDF, has surged from the supermarket into the energy market to supply UK homes with gas and electricity. Sainsbury aims to offer competitive prices and awards customers with Nectar Points.

Scottish & Southern Energy

Scottish & Southern Energy is comprised of Swalec, Scottish Hydro Electric and Southern Electric. Together, they supply gas and electricity to over 8,000,000 UK customers, and are the second largest supplier of energy in the UK.

Scottish & Southern Energy is also accredited with:

  • being the first UK energy supplier to scoop the 'No. 1 UK Domestic Electricity and Gas Supplier in Customer Satisfaction' for both gas and electricity in the JD Power and Associates survey

  • building the UK’s first deep water wind turbine in the Moray Firth

  • being the first UK energy supplier to hit the 100MW electricity threshold from a wind farm

Scottish and Southern Energy have also invested over £850 million in renewable generation, refurbishment and construction projects.

Note: The following energy brands are also part of the Scottish & Southern Energy Group.

Atlantic Electric and Gas started in October 2000 as an electricity provider before offering gas and dual fuel products.

Scottish Hydro Electric has been supplying energy to homes north of the border since 1947. It specialises in turning the Scottish weather into renewable energy, e.g. turning raindrops into hydro electric power at Glendoe or harnessing the formidable Scottish breeze at its wind farms.

SWALEC has provided energy to Welsh homes and businesses for decades. It employs around 1,200 people in Wales and maintains strong links with the Principality and its people.

Energy Providers: Want to Know More?

So, there you have it. Now you know who the ‘Big Six’ are and what they’re about, why not find if they can reduce your gas and electricity bills.

By switching energy providers, you could save big money on your utility bills.

Switch Utilities with


Tagged under:

Gas & electricity

Compare energy prices & switch suppliers with

Compare energy