A solar based biomass co-fired combined cycle with hydrogen production is proposed and assessed with conventional and modified thermodynamic and exergoeconomic analyses. The cycle uses biomass and solar energy as renewable energies along with the fossil fuel natural gas. Hydrogen is produced by the photovoltaic/thermal system and in one option is injected to the combustion chamber of combined cycle to reduce fossil fuel usage and CO2 emissions. Modified analyses are based on avoidable and unavoidable exergy destruction and component investment costs. Although hydrogen injection does not increase efficiencies, it reduces the exergy destruction by 0.24%, the total exergy destruction cost rate by 3.36%, the CO2 discharge rate by 2% and the total unit product cost by 3%. Based on conventional analysis, the gasifier, the post combustion chamber and the combustion chamber are the components with high exergy destructions, while based on modified analysis the combustion chamber, the gas turbine and the air compressor have highest exergy destructions. The components with the highest investment cost rates are shown to be the steam turbine, gas turbine and air compressor by conventional method while with the modified method they are found to be the gas turbine, the air compressor and the steam turbine. Crown Copyright (C) 2018 Published by Elsevier Ltd. All rights reserved.