Abstract With the rollout of proposed smart grid tariff structures in the Republic of Ireland the modelled role of an energy storage device in reducing the energy and economic loads of a public school building is presented. The school building has a 33kWp photovoltaic system, the performance of which is compared to other PV systems in the Irish environment. Concurrently, a Zinc Bromine flow battery has been operated under various charge and discharge rate cycles and the overall energy performance of this system has been virtually matched to the output of the PV. The scenarios trialled include ‘business as usual’ modelling the economic impact of smart grid tariffs versus a flat rate tariff as currently operation with PV in situ; a ‘peak shifting’ scenario where the battery operation is linked solely to the smart grid tariff rates and ignores PV resource and a ‘PV optimisation’ scenario where the PV output is considered ‘free’ energy and as such has priority in storage. The three scenarios show that the greatest economic impact comes from the ‘PV optimisation’ scenario, which is mainly related to PV generation at low economic value times.