India can potentially save Rs 89.4 billion ($1.2 billion) a year by shutting down some old coal-burning power plants and allowing newer ones to run for longer hours, a study says ( https://bit.ly/3yLrdeT ) . An interesting perspective indeed. But economically, there could be a challenge: While the economics of old coal plants might work because of full depreciation, new coal plants might find it difficult to compete against the fast decreasing costs of renewable power.