Understanding photovoltaic (PV) cell operation relies on accurate models being available that follow practical PV characteristics. Many models are proposed in the literature that vary in their complexity and range of application. This paper investigates the key issues involved in developing an accurate PV cell model that can demonstrate the effects of environmental factors. Operational constraints and other factors such as irradiance, temperature and partial shading are discussed. Additionally, models and parameter estimation techniques proposed in the literature are explored in detail to assess their suitability in modelling a commercial PV array. Experimental results are also provided.