A global economic analysis methodology is proposed in order to simplify the cost and the pro®tability assessment of energy and services delivered by photovoltaic (PV) systems. As examples, equations and graphic tools derived from this methodology give directly the overall discounted cost (ODC) of electricity delivered by grid-connected PV power plants and the ODC of water delivered by a stand-alone PV pumping system. The main criteria used for pro®tability analysis of PV projects are reviewed: net present value, internal rate of return and pro®tability index (PI). A simple method with associated equations and graphic tools is presented in order to assess the pro®tability of PV projects from their PI. Examples of pro®tability analysis of present and future grid-connected PV power plants built and operated by an independent power producer are presented and discussed, together with examples of stand-alone PV water pumping systems operated by the local community in developing countries. In both cases, equations and speci®c graphic tools are presented. Speci®c graphs can be used with dierent monetary units, dierent sizes and dierent investment costs of PV projects.