We investigate whether photovoltaics (PV) can effectively and economically contribute to a massively renewable energy (RE) power generation future for Switzerland. Taking advantage of the country’s flexible hydropower resources, we determine the optimum PV/battery configurations that can meet the country’s growing electrical demand firmly 24×365 at the least possible cost while entirely phasing out nuclear power generation. We examine several ultra-high RE scenarios where PV and hydro would meet the bulk of the country’s demand. Depending on future cost predictions for PV and batteries, and a small contribution from domestic or imported dispatchable resources, we show that power production costs on the Swiss grid would range from 6 to 8 cents per kWh. This is well in line with market prices till mid-2021 and strongly below the current price levels. Also, scenarios with no or only marginal imports – either of electricity or e-fuels – would lead to only slightly higher costs – due to the effects of overbuilding and curtailment. Our analyses show that firm PV power is an enabler of the energy transition and can ease the energy trilemma – regarding security of supply, sustainability and affordability – existing also in Switzerland.