Indonesia is a country with a growing population of 270 million people and a land area of 1.9 million km2. Because Indonesia is a tropical country, solar insolation has low seasonal variation, with 4.8 kWh/m2/day on average. The wind resource is small compared with the solar resource. Relatively small amounts of hydro, geothermal and bio energy are available. Contrary to its huge renewable energy potential, Indonesia still much depends on fossil fuel, nearly 90% of total generation. The national renewable energy target for Indonesia in 2050 is only 31%. Many views have been expressed that 100% renewable energy is too expensive or that there is insufficient space for wind and solar collectors. The study presents the prospect for 100% renewable electricity in Indonesia in 2050, mainly through the use of solar photovoltaic. This study finds that the demand of 3000 TWh per year will be satisfied by 1800 GWp solar PV capacity, which is supported by 8200 GWh off-river pumped hydro storage capacity. The cost of a 100% renewable electricity system for Indonesia with sufficient storage to balance in every hour of the years is found to be approximately US$48 per MWh. It is much lower than Indonesia’s current generation cost which was US$79 per MWh in 2018.