Tim Jarvis, director general of markets at Ofgem, said the drop in energy bills reflected a fall in the international price of wholesale gas.
Mr Cole said he suspected prices would go up again in the winter, as demand for fuel rises again across Europe.
He said he would like to see the energy price cap, which sets a maximum that suppliers can charge for each unit of energy, reviewed every six months, instead of the current three months, to give consumers more certainty.
His charity supports people struggling to pay their energy bills and he said they often said they were worried about future price rises.