The implementation of the quarter-hourly market (QH) in the Spanish electricity sector is a significant change that allows for more accurate allocation of deviations and more optimised operation of the electricity system. However, it requires agents to adapt their forecasting, operation and settlement systems to handle these more granular intervals.

From 1 May onwards, deviations will be settled on the basis of fifteen-minute granularity, in accordance with the Resolution of 28 March 2025 of the Secretary of State for Energy.

This marks the end of the transitional period during which REE has settled deviations by applying the same measurement to all fifteen-minute periods. Starting in May, settlements will be made on an hourly basis, either using actual meter data or interpolations, at all production facilities and consumption points in the electricity system.

This new update to the electricity system means that forecasting systems will also require hourly interpolation to quarter-hourly, so that the different market agents can adjust their positions in the intraday market, define fortnightly programmes and reduce the impact of deviations.

Below, we provide you with the keys to ensuring that these forecasts meet the new market requirements.