Abstract We formulate the concept of a multi-functional energy system, called storage plant, as a possible solution to cover the variable residual load that appears in most countries after introducing renewables in the power sector. A storage plant consists of a photovoltaic power plant, a heat storage system with electric heater to transform solar power, a steam power cycle to convert stored heat to dispatchable power, a backup heating unit for the storage based on the combustion of biomass or other renewable hydrocarbons, and a gas turbine with waste heat recovery for peak loads. After explaining the storage plant concept, the paper describes a simulation model of the German power sector and its transformation from the year 2020 with roughly 40% renewable electricity share to 2040 with a hypothetic 90% renewable electricity share. Multi-indicator benchmarking over that period shows that storage plants can have a key role to achieve emission goals and at the same time sustain full supply security within the German power sector.