Abstract This paper presents a critical view of Florida's photovoltaic (PV) subsidy system and proposes an econometric model of PV system installation and generation costs. Using information on currently installed systems, average installation cost relations for residential and commercial systems are estimated and cost-efficient scales of installation panel wattage are identified. Productive efficiency in annual generating capacity is also examined under flexible panel efficiency assumptions. We identify potential gains in efficiency and suggest changes in subsidy system constraints, providing important guidance for the implementation of future incentive programs. Specifically, we find that the subsidy system discouraged residential applicants from installing at the cost-efficient scale but over-incentivized commercial applicants, resulting in inefficiently sized installations.