CHENNAI: Due to a hike in natural gas prices, the cost of power generated by State-owned gas power plants has gone up from Rs 3 to Rs 7 a unit and Tami Nadu may have to spend Rs 650 crore more this year to generate power from these plants. State-owned gas power stations generated 1,700 million units of electricity in 2021-22 financial year at a cost of Rs 550 crore.The price of natural gas, which stood at $2 a Btu (British Thermal Units) till March 31, has gone up to $6 on April 1.