The proliferation of the use of Photovoltaic PV systems, as one of the sources of electricity that comes from renewable energy resources, attracting the researchers to investigate on the factors that have an effect on the performance of it. This paper presents an analytical study for evaluating the performance of PV system that generates 2.5 kWp through the deployment of this system to supply the electricity for the Engineering Consultant office, of the College of Engineering at Wasit University, Iraq (32.497 N, 45.842 E). The evaluation is conducted by monitoring the pre-defined system which consists of 10 PV modules as an array of two rows. The system is supervised for six months from 1st of Feb. until 31st of July, to assess the impact of temperature, shading, and dust on its’ output power and performance. The PV array is omitted to 8˚ south-west, and 40˚ in elevation. The results shows that the PV array is operated at efficiency of 12.12% and the maximum efficiency reached 13.01 during April. The average daily power of it, for the months from Feb. until July are: 1.347 kW, 1.421kW, 1.436, 1.215 kw, 1.045kW and 1.042 kW, respectively. The minimum average output power is recorded in summer season (June and July), because of the high ambient temperature in these months. The maximum reduction of power due to shading at 4 pm is 52.77% in February followed by March 47.7 % and April 22.93 %, while the maximum reduction in efficiency due to shading were 51.82 %, 44.71%, 23.01% in February, March and April, respectively. The reduction in power due to the dust accumulated after 54 days exposure to environments conditions was 7.88%.