Chris Gauld, 35, who was Spark's first sales director and has been managing director since 2009, takes over at the helm in succession to Canadian-born entrepreneur PJ Darling who created the business.
Mr Darling will remain a substantial shareholder and a mentor to the company. Spark chairman Sir Timothy Noble said: "After setting up the company in 2007 and guiding it to its present position, PJ has decided he wishes to revert to the role of being an entrepreneur in a small business again. The fact that the company now has close to 100,000 properties supplied, a likely turnover of £80 million this year, and over 200 employees is a tribute to his vision."
Sir Timothy went on: "Spark must be almost unique in Britain in having raised equity investment of more than £12m over the last five years to finance its progress and also survive financial storms." In January, Spark Energy unveiled a landmark deal with Morgan Stanley Commodities for wholesale energy supply combined with long-term hedging on favourable terms.
The group supplies the largest high street letting agents in the UK as well as online and prepayment customers.
Mr Gauld said: "This is a difficult time to be running an energy company, especially at the smaller end of the scale, but we are greatly encouraged by Ofgem's recent initiatives to increase transparency of the wholesale trading arrangements of the Big Six, to increase speed of switching for customers and to increase competition generally."
He said Spark was forecasting a £130m turnover next year helped by new products, technologies and markets, adding: "Small suppliers have a critical role to play in improving the choice, service and transparency which the industry has been lacking in the past."