The company, whose customer base of 150,000 is dwarfed by the Big Six firms who dominate the UK market, said it was absorbing some of the spiralling costs of buying wholesale energy as it increased prices by an average 4.5%.
It said the rise would not apply to existing energy users until January but would hit all new consumers from October 21.
Co-Operative Energy said the increase equated to an extra £4.78 a month for an average dual fuel customer, who would now pay £1,315 a year - but this was still £87 a year less than a British Gas bill.
It comes after Centrica-owned energy giant British Gas announced it was hiking electricity bills by 10.4% and gas tariffs by 8.4% - affecting 7.8 million households - while SSE recently announced it was hitting seven million customers with an 8.2% rise.
Both blamed a combination of Government green levies and rising energy costs for the increases. British Gas said the profits it made were crucial in funding investments. But Centrica also paid £816 million shareholder dividends last year, a rise of 7%.
The company said i t is now calling for other suppliers to follow its lead and put customers before profits.
General manager Ramsay Dunning said: "We pledged to offer fair pricing and even after this increase we will still be competitively priced against the big suppliers' standard tariffs.
"We are not increasing prices to reward financial investors, but to ensure we continue to run a sustainable business for our members."