Optimal pathways to 100 % renewable energy in Nepal: A least-cost assessment of solar PV, hydropower and pumped hydro energy storage integration

• Explores least-cost 100 % renewable energy transition pathways for Nepal by 2050. • Uses hourly, non-linear optimization across 12 future demand and hydro scenarios. • Solar PV dominates generation; PHES ensures seasonal and daily balancing. • LCOE ranges from $56 to $114/MWh; import reduces the storage needs and cost. • Supports long-term renewable energy policy, planning and system investment decisions. Nepal has vast renewable energy potential yet continues to rely heavily on traditional biomass and fossil fuels, with per capita electricity consumption at just 0.4 MWh/year. This low level of electricity usage highlights the need for a long-term electrification strategy that enables broader energy transition. This study explores pathways to 100 % renewable energy by transitioning end-use sectors to electricity, using an hourly energy balance model of Nepal’s future electricity system by 2050. Solar photovoltaic (PV) and hydropower are modelled as the primary energy sources, while pumped hydro energy storage (PHES) and cross-border electricity imports are used for system balancing. Twelve scenarios are analysed for 2050, incorporating three electricity demand levels (2, 5, and 9 MWh per capita per year), two hydropower development pathways (reference and ambitious), and scenarios with or without electricity import. Results indicate that solar PV is the dominant generation source across most scenarios, while PHES plays a vital role in both daily and seasonal balancing. The levelised cost of electricity (LCOE) ranges from $56/MWh to $114/MWh, depending on key assumptions. Sensitivity analysis reveals that solar PV costs, discount rates and hydropower development pathways are key economic drivers. These findings demonstrate that Nepal’s future energy demand can be met largely with mature, proven renewable technologies. These insights are valuable for long-term energy planning and offer guidance for other countries with similarly low electricity usage. It also contributes to progress towards the sustainable development goals (SDGs), mainly SDG 7 (Affordable and Clean energy) and SDG 13 (Climate Action).