A method for operating a hybrid power plant comprising fuel-operated heating and solar energy heating of carrier fluids, wherein a first portion of total power provided by the power plant is based on fuel-operated heating of carrier fluids and a second portion of the total power is based on solar energy heating of carrier fluids, the heat absorbed by a solar energy heated carrier fluid is transferred to a carrier fluid circuit of a fuel-operated part of the power plant. When a sudden increase or reduction of the total power provided by the power plant is required as compared to a basic state, the second portion is first increased or reduced over a short time period in order to provide a positive or negative reserve power. Subsequently, the first portion is slowly increased or reduced and the second portion based on solar energy heating is correspondingly reduced or increased again.