This paper deals with the modelling and analysis of a photovoltaic (PV) electro-chlorination system and compares the amount of electric charge and chlorine output delivered to systems when operating with and without a maximum power point tracker (MPPT). Results show that good performance of the electrolytic system load is obtained if the intersection is to the left of the maximum power locus of the PV array. Based on this property a simple rule of sizing the PV array may be adopted. Using an MPPT in the system would be advantageous to boost chlorine production. Field trials indicated that the daily and seasonal variations in solar radiation match well the need for chlorine production during the day. Using PV for salt-water chlorination is an effective way to semi-automate the input of chlorine into the swimming pool and offers a cheaper alternative to mains power chlorination.