What Astrid means is thatsome panels onlyhave roughly an 8-10 year average life span.... the photovoltaic cells in them die and you need new panels....so you want to make sure you are getting the best quality panels for your money not cheap crap that is going to die after 5 years or something like that. You have to think of solar just like any other appliance...it is not a once off cost, it will need replacing just like a hot water service or washing machine etc etc....