Techno-economic insights on solar PV + storage in Small Island States (SIDS): Evidence from Trinidad and Tobago

Small Island Developing States (SIDS) struggle with high electricity costs, fossil fuel dependence, and climate-related supply risks, yet empirical cost data for solar PV plus battery storage remain limited. This study addresses that gap using competitive tender prices and detailed PVsyst performance simulations from six recently commissioned grid-connected hybrid systems in Trinidad and Tobago (2–10 kW PV; 15–30 kWh storage). Results highlight pronounced economies of scale, with system size expansion from 2 kW to 10 kW reducing the levelised cost of electricity (LCOE) from US$0.694/kWh to US$0.191/kWh (−72 %) and levelised cost of storage (LCOS) from US$0.284/kWh to US$0.186/kWh (−34 %). Marginal abatement costs simultaneously decrease from US$211 to US$66 per tonne CO₂, reflecting substantially improved environmental returns with increased system scale. Lead-acid batteries offer lower upfront costs; however, lithium-ion storage approaches cost parity at system capacities of 5 kW or greater due to superior cycle life and utilisation characteristics. Despite these improvements, the resulting costs remain significantly above global benchmarks, highlighting structural economic and logistical challenges specific to SIDS contexts. Key policy recommendations include aggregating rooftops into optimally sized installations (8–10 kW), deploying targeted green financing mechanisms, and introducing dual-rate net billing tariffs coupled with storage rebates. Implementing these policies can significantly reduce unit costs, narrowing the gap with global benchmarks, and provide a replicable framework for sustainable renewable energy deployment and carbon mitigation in SIDS.