Commercial steel roofs are an attractive platform for building-integrated photovoltaics (BIPV).The potential advantages include the reduction of labour and materials when contrasted to a building-attached system.This system and electricity cost reduction can be more than 25%,which will make this solar-generated electricity less expensive than grid electricity in all of Australia and many other locations.We are developing a building-integrated photovoltaic (BIPV) roofing material to be factory-integrated with low-cost steel roofs for commercial buildings.This roofing product is based on the ultra-thin silicon on steel (UTSi) solar cell.It is being developed in collaboration with AmberWave Inc.based on epitaxial growth of a thin layer of monocrystalline silicon grown on porous silicon.Efficiencies of up to 16.8% on 4cm2 devices and 15.9% on 88cm2 devices have been demonstrated to date,both with an active layer thickness of just 18 μm.The near-term solar cell efficiency potential of the UTSi solar cell is well above 20%.Details of the solar cell and its value when applied to a steel roof component will be described.