A series of mergers in the energy market have led to a change in the Big Six.
Ovo has increased its market share by 14.5% after taking on SSE.
Octopus Energy has also increased its share by recovering Engie customers.
Scottish Power took on 130,000 customers from failed supplier Tonik Energy last week, increasing its market share considerably.
As of 31 July 2020, Scottish Power held an 8.7 per cent share of the UK energy supply market and Tonik Energy had 0.6 per cent, meaning the Big Six supplier now has a 9.3 per cent share.
Tonik went bust as it was revealed it was one of seven suppliers that had not paid a combined £34million it owed to Ofgem. It is just one of a slew of small energy firms that have ceased to trade in the last couple of years, including Breeze, Economy, Solarplicity and Spark.
When these suppliers fail, other providers grow as they take on the stranded customers ena masse, as prvoided for by Ofgem's Supplier of Last Resort process.
Mergers and acquisitions have shaken up the sector recently, with Ovo Energy's acquisition of SSE meaning its market share climbed to 14.5 per cent.
The supplier took over SSE in January 2020, becoming the second-largest energy firm in the UK in the process.
Similarly, Octopus Energy is now one of the biggest challenger providers, holding 5.7 per cent of the domestic market following its acquisition of Co-op Energy in August 2019 and ENGIE in January 2020.
Octopus is still considered a medium-sized supplier - one that has more than 250,000 energy accounts. The chart above shows how the shares of suppliers like Octopus have changed.
Due to this recent growth, it seems Octopus Energy will soon be one of the Big Six suppliers.
It is not just Octopus that's growing though, with Bulb and Npower both holding a similar market share, meaning growth and losses over the next six months will determine a clearer position.
These were the top six biggest energy providers in the UK five years ago by number of customers.
1. British Gas
5. Scottish Power
These are the top six biggest energy providers in the UK as of today by number of customers:
1. British Gas
3. EDF Energy
6. Scottish Power
In the year to July 2020, it is EDF Energy that has seen the highest net gain of the large suppliers, recording a 1.1 per cent increase in market share - despite its energy share being relatively similar between its two acquisitions.
One of the biggest increases in market shares would be from the merger of Eon and Npower whose combined market share would reach 16.6 per cent. Eon bought Npower's German owner Innogy in September last year after Npower lost 708,000 customers in 2019.
However, while the merger has completed, they are still being reported as separate brands as the supply business are being managed separately.
The two firms together still do not account for the highest market share which goes to British Gas with 22.1 per cent of customers. It increased its number of customers after taking on those of Robin Hood Energy after it collapsed.
Nottingham city council's failed provider agreed to sell thousands of customer accounts to British Gas, resulting in 112,000 households and 2,600 business customers being transferred to the Big Six supplier, five years after Robin Hood Energy was set up.
Katie Hickford, Analyst at Cornwall Insight, said: 'Acquisitions and mergers have been the biggest form of supplier growth, with 10 instances of trade sale events in the domestic supply market since January 2019.
'Alongside this was also 10 exits through the supplier of last resort process.
'Of the gaining suppliers, the greatest level of activity was seen across the medium supplier group, consolidating their position among the largest 17 suppliers by customer number.
'The medium supplier group took on nine acquisitions, with Octopus Energy the most active, growing its customer base by an estimated 375,000 customers.
'Octopus Energy has gained a collective 1.5 per cent market share through its trade sale acquisitions.
'However, it is Octopus Energy's recent organic customer growth that sees it become the sixth-largest supplier in the market.
'Some larger suppliers have also been active with EDF Energy and British Gas the most active in domestic supply acquisitions in 2020.
'Despite market share growth for some suppliers this quarter, it is currently a challenging environment for suppliers due to Covid-19, and some impacts have still yet to be seen.'
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