Rise to power In just four and a half years, PowerStream has grown to become the second-largest electricity distributor in Ontario. Ben Sansom charts this upward mobility. PowerStream is a household name in the province of Ontario. Providing electricity to businesses and homes in Barrie, Vaughan, Markham, Richmond Hill and Aurora and to seven other communities in Simcoe County and York Region, it is jointly owned by the cities of Barrie and Vaughan and the town of Markham.