Solar panel systems that are mounted on a roof have no moving parts that can wear out, break or need to be replaced. Solar panels do not produce noise or harmful emissions of polluting gases. Solar panels therefore guarantee years of carefree sustainable energy supply. There are many advantages to solar panels on roofs. For example, roof mounting offers the possibility of supplying energy directly where it is needed, and there is no need to use scarce space – such as agricultural land. Interestingly, if solar panels were installed on 40% of Dutch roofs, enough energy would be generated to supply the whole of the Netherlands with electricity.