Co-benefits and cost-benefit analysis of energy transition in the power sector in China and India

China and India, two of the world's leading carbon emitters, have pledged to achieve carbon neutrality by mid-century in alignment with the Paris Agreement. Central to this ambition is the electrification of their economies, and both nations have made significant strides in recent years. Yet, a thorough cost-benefit analysis of their energy transition progress and future energy transition pathways remains lacking. Here we adopt nine comprehensive models to assess the region-specific co-benefits related to carbon emission, air pollution, health and employment of energy transition in the power sector in China and India from 2015-2020 and further explore their most cost-effective pathways towards 1.5°C and 2°C scenarios in 2030-2050. We find that although the emissions contributed by the power sector in China and India from 2015 to 2020 resulted in more than 10,000 PM_2.5 attributable deaths in 2020, the economic benefit of job creation of new installation of renewable power in 2020 was 68 (95% CI: 56-93) times and 6 (95% CI: 5-7) times than the monetary of health loss. Under the SSP1_RCP2.6 scenario, it will ultimately achieve the largest benefit (monetary health co-benefits) to cost (carbon mitigation cost) ratio for both countries in 2050, and India (14.6 (95% CI: 12.7-16.1) will obtain a larger ratio than that of China (4.1 (95% CI: 3.3-4.7)). We recommend both nations deepen their commitment to power sector transition, prioritizing low-carbon fuels and expanding education and skill training to support the emerging new energy economy.