In this study, we considered the case of decarbonizing Ukraine's electricity sector that has significant import dependence, high energy and carbon intensity, and an unprecedented destruction of electricity facilities due to ongoing war. Using a newly built UKRAINE-EXPANSE model, which covers 24 Ukrainian oblasts (regions) and five neighboring countries at high temporal and spatial resolution, we offered four cost-optimal scenarios for the national electricity sector in 2035. Considering the targets of the current National Energy and Climate Plan and the Updated Nationally Determined Contribution of Ukraine to the Paris Agreement, we analyzed the structure of the installed capacities, annual electricity generation, storage, transmission, and trade with neighboring countries and calculated sustainability impacts (greenhouse gas and air pollution emissions, employment, land use, and total system costs). We showed that in 2035, the undamaged total installed capacity (as of May 2024) should be increased by 2.7-3.2 times while supplying up to 16.3% higher electricity demand compared to the pre-war period. Nuclear and gas power would still remain the primary electricity sources in 2035, supported by intensive growth in wind power, pumped hydropower storage, bioenergy and expansion of transmission grids. Implementing environmentally friendly scenarios with 30% of renewable generation and/or no hard coal power would require only 5 to 13% higher total system costs compared to the least cost scenario, which could be socially and politically acceptable.