A decarbonized economy implies deep structural changes across industries, including the power system, whose operation needs to balance supply and demand instantaneously. The energy planning community usually work with hourly-resolution tools, while the integrated assessment community do so with the year as the time unit. This article describes a model that integrates both time frames to consider limitations and competition among suppliers of electricity in long-term scenarios, with Spain as the case of study. The calibration was carried out over four historical years (2017-2020, including the impact of Covid) to show both the sensitivity of different meteorological conditions and differences in the ranking of priorities to supply power. The results show values below Spain’s objective of 74% presence of renewables in the electricity mix in 2030; while this objective is reached by our own proposal.