Electrothermal performance and environmental effects of optimal photovoltaic–thermal system

•Feasibility study in off-grid PVT system for supply of a household demand is done.•PVT system, battery, and thermal storage tank is modeled and optimized using GA.•Irradiation is calculated considering climatic conditions using actual data.•Optimal angles of locating system for maximum solar power absorption are obtained.•Scenarios for raising efficiency is proposed and environmental effect is discussed.