Apart from many other factors the overall performance of PV depends on temperature and solar irradiance because as the day progresses the energy received by PV panels from the sun changes and temperature also changes throughout the day. In this paper effects of temperature and solar irradiance variation were studied on a 240V PV panels maximum power, efficiency, and fill factor. The model is designed in Simulink/Matlab software which has two variable inputs in the form solar irradiance and temperature and three output parameters i.e. efficiency, fill factor and maximum power. First the performance parameters are observed under STC conditions and then one of the input is changed from STC whereas the other one is kept constant. At the end the second input is varied whereas the first one is held at STC. Simulations were performed and results obtained in terms of maximum power, efficiency and fill factor shows percent variation from its reference value for every one degree centigrade change in temperature and for every 20W/m2 change in the solar irradiance.