TransAlta Corporation (formerly Calgary Power Company, Ltd.) is an electricity power generator and wholesale marketing company headquartered in Calgary, Alberta, Canada. It is a privately owned corporation and its shares are traded publicly. It operates 75 power plants in Canada, the United States, and Australia. TransAlta operates wind, hydro, natural gas, and coal power generation facilities. The company has been recognized for its leadership in sustainability by the Dow Jones Sustainability North America Index, the FTSE4Good Index, and the Jantzi Social Index. TransAlta is Canada's largest investor-owned renewable energy provider. The company is not without controversy as the Alberta Utility Commission ruled in 2015 that TransAlta manipulated the price of electricity when it took outage