The company, which has tripled customer numbers to almost 150,000 in a year, raised its tariffs by 4.5%, about half the rate of some of its Big Six rivals, earlier this month.
It recorded sales in the six months to July 27 of £75 million. A spokeswoman said this represented gross sales growth of more than 600%.
The supplier was launched in May 2011 with a call for a "radical shake up" of the industry and boasts that it pledged a price freeze during the most recent winter months - at a time when rivals had raised theirs.
Co-operative Energy is wholly-owned by customers and shares out surplus profits among members. It says it is shouldering part of the burden of spiralling costs to lessen the impact on customers.
It is part of the Midcounties Co-operative, which announced overall sales up by 36% to £593 million for the half-year period - attributed to strong performance from its energy division as well as childcare and travel.
Co-operative Energy has challenged the larger energy firms over prices, amid a pledge by Labour leader Ed Miliband to freeze tariffs should he win power.
Meanwhile, Mr Miliband has said he switched from E.On, one of the Big Six, to another small supplier, First Utility after being stung by a bill for £1,000.