From 18 March 2025, the Spanish electricity market will take a decisive step towards greater operational granularity with the implementation of the intraday market in 15-minute intervals (QH) and the settlement of deviations at the same resolution (ISP15).

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.