This article presents a methodology of showing the rate of integration of specific renewable energy sources (RESs) into the electricity supply system. The methodology is used on large-scale integration of wind, photo voltaic and wave power into a future Danish reference energy system. The possibility of integrating RES into the electricity supply is expressed in terms of the ability to avoid excess electricity production. The different sources are analysed in the range of an electricity production from 0 to 100% of the electricity demand. The excess production is found from detailed energy system analyses on the computer model EnergyPLAN. The analyses have taken into account that certain ancillary services are needed in order to secure the electricity supply system. The conclusion is that different patterns of each of the RES can be shown in terms of excess electricity diagrams. Such diagrams do not differ from one year to another, but do differ from one RES to another.