The increasing solar photovoltaic (PV) generation highlights the importance of PV systems’ scalability, reliability, and cost reduction. Herein, a modular fault‐tolerant PV multistring inverter to address this challenge is proposed. The proposed inverter features a modular dc‐dc conversion stage and a dc–ac conversion stage. This configuration allows scaling the inverter power rating by simply increasing the number of PV strings, associated dc‐dc modules, and dc–ac‐stage heatsink size and output‐filter inductances’ current rating. The fault‐tolerant capability allows for tolerating a first‐switch open‐circuit fault on either stage and continuing operation. This property allows increasing by half the inverter lifetime compared with nonfault‐tolerant solutions (dismissing inverter reparation and degraded mode of operation), with a low impact on the cost increase (3–7%) and an efficiency reduction after a fault occurs of only 0.33–1%, depending on the module count and fault localization. A generalized reliability assessment demonstrates that lifetime increase is achieved regardless of the number of modules. Additionally, it allows reducing the operation and maintenance costs and revenue losses due to unscheduled system shutdowns. To validate the proposed inverter, a lab–scale prototype with two modules is tested under emulated faults, validating the feasibility of the proposed inverter.