More than 40% of coal-fired power plants in China — the world’s biggest producer of the fossil fuel — are losing money, according to an innovative new study.

The analysis, from climate think-tank Carbon Tracker, uses satellite data to gauge power-plant use in a country where official statistics are unreliable. It offers a fresh way to gauge the scale of China’s well-known overcapacity issues in coal supply and generation — and establish which firms are most exposed as the government cracks down.