To meet climate goals, countries must decarbonize their electricity systems. Yet, uncertainty in future technology costs, electricity demand, and renewable energy generation complicates power system planning and makes the affordability of clean electricity uncertain. Here, we develop a multi-model framework to examine cost-optimal pathways for generation, storage, and transmission expansion in India under alternative technology costs, electricity demand projections, and clean energy and carbon-emission targets. Across all scenarios, real average system costs remain below 2020 levels throughout 2030-2050, even when carbon emissions decline linearly to 90\% below current levels by 2050. Solar PV comprises over half to three-quarters of total installed capacity by 2050 supported by large-scale deployment of short-duration battery storage. Expanding green hydrogen, pumped hydro storage, and nuclear reduces costs by less than 2\%, whereas demand response lowers costs by up to 10\%. Declining renewable and battery costs, together with demand response, make deep electricity decarbonization affordable across a range of realistic scenarios.

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