The European Solar Telescope (EST) is a European collaborative project to build a 4m class solar telescope in the Canary Islands, which is now in its design study phase. The telescope will provide diffraction limited performance for several instruments observing simultaneously at the Coudé focus at different wavelengths. In order to guarantee the achievement of the demanding scientific requirements, error budgets of main performance have been defined from the early design study phase in top-down fashion. During the design study, analyses are being performed in order to update the defined error budgets in bottom-up fashion. Error budget management is proposed from the design study phase to be used during the complete project life cycle.