This study presents the performance assessment of grid-connected PV system installed on the roof of a building. The results presented were based on data recorded from March 2013 to February 2014. The total annual energy output delivered to grid was found to be 1927.7 kW h, with an annual specific yield of 931.6 kWh and monthly average energy output of 160.6 kW h. Furthermore, the annual average daily array yield, final yield and reference yield of the PV were estimated as 2.73 kW h/kW(p), 2.55 kW h/kW(p) and 2.80 kW h/kW(p), respectively. In addition, the annual average daily PV module efficiency, system efficiency and inverter efficiency were 12.7%, 11.6% and 88.8%, respectively. The overall annual capacity factor, system losses and performance ratio were found to be 10.58%, 16.96% (with respect to reference yield) and 83.03%, respectively. The findings from this installation indicate that PV-connected system is technically feasible for electricity generation in Norway and could a play role in the future energy mix of the country. (C) 2014 Elsevier Ltd. All rights reserved.