Increasing installation of photovoltaic (PV) systems and demand for more accurate prediction of their operational performance in the UK has prompted the research that aims to establish the relationships between output efficiencies, weather parameters and deposited solid particles on the panel surface. The direct use of efficiency figures quoted by PV manufacturers, normally based on measurements taken in clean laboratory environments of 25 degrees C and at standard air density, is often not appropriate as field studies demonstrated the actual outputs could be reduced by as much as 60% in dusty or polluted climate without regular cleaning. The experimental investigations and case studies took place in the town of Brighton in the southeast of the UK. Experimental simulations of dry dust cover were carried out in the laboratory to establish the effect of dust density to light transmittance. The effect of dust deposit on panels subjected to the climatic elements was studied using a set of outdoor glass units configured at different tilt angles placed on a roof, which were subsequently analysed in the laboratory after exposures between one and four weeks. Effects of climatic parameters on the performance of PV panels were examined through detailed analysis of the performance of two existing PV installations in relation to their weather exposure. Results for the indoor experiments showed that even a small amount of fine particles could reduce light transmittance by as much as 11%. Distribution analysis of dust collected from the exposed glass units revealed particles sizes were smaller than 400 microns with the highest frequency under 20 microns but the impact on solar transmission through the glass was mere 5% after exposure of four weeks due to the frequent rainy days. Amongst a wide range of climatic parameters used in the statistical analysis, high humidity, rain and snow were found to have significant effects to the efficiencies of the two PV installations, which in some cases could annihilated any system output. This study has also revealed the geographical issue of birds in this coastal city as their droppings can create overheated spots on the PV panel and reduce its output. (C) 2014 Elsevier Ltd. All rights reserved.