The Chilean Energy Policy calls for 15 percent of new power generation capacity to come from renewable energy sources from 2006 to 2010, and then a 5% of electric energy generated from renewable energy sources with gradual increases in order to reach 10% by 2024. Neither the government nor the power generation sector plans mention solar energy to be part of the renewable energy initiative. Part of this apparent lack of interest in solar energy might be due to the absence of a valid solar energy database, adequate for energy system planning activities. Monthly means of solar radiation are used in order to estimate the solar fraction for a 100 MW plant for four given locations. Our analysis considers two cases: operation during sunlight hours, and continuous operation during 24 hours a day. A net energy analysis for concentrated solar power (CSP) plants in Chile is then performed, considering the energy costs of manufacturing, transport, installation, operation and decommissioning. The results indicate that the CSP plants are a net energy source in three of the four locations, when operating in sunlight-only mode. This is due to the lower radiation levels available at that location, which implies a high fossil fuel back-up fraction. In the continuous operation mode, the CSP plants become fossil fuel plants with solar assistance, and therefore all locations display negative net energy. Based on this result, the back-up fraction required for the plants to be net energy sources is estimated from the EROEI as function of the back-up fraction. It is estimated that the net energy analysis is a useful tool for determining under which conditions a CSP plant becomes a net energy source, and thus can be utilized in order to define geographical locations and operation conditions where they can be considered renewable energy sources.