A company that sells electricity online made the biggest gains in a month when large numbers of customers switched companies.
Figures from the Electricity Commission show almost 35,000 customers left their supplier in March, in favour of a cheaper option. The number was a nine year high.
The small online company, Powershop, added more than 2000 new customers to its existing 10,000.
Powershop says having low overheads means it can offer cheaper prices.
Chief executive Ari Sargent says customers are able to log on and check their readings, giving them more control over how much electricity they use.