Energy supplier switching hit an unusual low last month after only 418,000 customers changed supplier. This is four percent less than May 2020 and the lowest monthly switches completed outside of the annual January dip since July 2017.

More than 2.5 million switches have completed so far in 2021.

Changes of Supplier (CoS) started in May 2021 was also similarly low with the month ending on 508,000. This is one percent up year-on-year as last May was right in the middle of the first Covid-19 lockdown but is atypically low for the time of year. Other than April and May 2020 (and January this year which was the start of the second Covid lockdown), May 2021 was the lowest non-December month for new CoS events since February 2017.

Based on recent switching activity, our Energy Market Insights experts predict around 450,000 switches completed for the month of June – similar to June 2019. However, recent news about a large supplier increasing their prices this month potentially signals a larger shift in CoS across other non-large legacy suppliers in the latter half of the month.

In terms of switches according to supplier types, the only category that increased compared to May last year was large supplier to large supplier switches. All other types remained the same or decreased.

  • Large to Large CoS reached 199,000 – four percent more than May 2020 and 48 percent of May 2021’s total switches completed,
  • Large to Other CoS reached 122,000 – seven percent less than May 2020 and 29 percent of May 2021’s total switches completed,
  • Other to Large CoS landed at 57,000 – the same as May 2020 and 13 percent of May 2021’s total switches completed, and
  • Other to Other CoS hit 41,000 – 25 percent less than May 2020 and 10 percent of May 2021’s total switches completed.

Gains analysis – who is winning in the retail energy market

The recent dominant pattern of net gains – where all other supplier types make gains at the expense of the large legacy suppliers – continued in May. Over the last three years, the large legacy brands have been losing customers to other suppliers at a rate of 1.5 million (or five percent of the market) a year. The market share of the remaining large legacy suppliers stood at 55 percent at the start of April 2021, which could decrease to under 50 percent next year. However, that does not account for acquisitions made through Supplier of Last Resort events or trade sales.

Except for last month, the most popular switch type in 2021 has been from large legacy to other large suppliers, replacing switching between large legacy suppliers as the most popular type. (Note: SSE under Ovo is still a separate brand, but it is no longer presumed as part of the former Big Six and its gains are counted in the large legacy to other large category.)

The biggest net winners last month (and that’s true of eight of the last 12 months) were small suppliers and the third most popular switch type for most of the last year has been large legacy to small challengers.

This is to be expected as large legacy suppliers still have the most customers to lose. The large legacy suppliers’ market share is decreasing and there are more small suppliers than any other supplier type. This also potentially demonstrates that an established name is not necessarily the key driver of customer preference.

For more information on CoS figures, contact [email protected]. If you would like access to the CoS data we hold and analysis we provide for the energy market, please reach out to [email protected].



The above figures relate to electricity CoS in Great Britain only.

We do not include CoS from Supplier of Last Resort (SoLR) processes or trade sales in our monthly CoS reporting. We account for only voluntary switches, or instances where the customer made an active decision and took action to change supplier.

CoS started refers to the number of valid switches started, also known as CoS raised.

All data is provided by ElectraLink’s EMI from the EMDH.

ElectraLink has been granted the governance protections to hold, transfer and analyse CoS and other data.