This article is intended to analyse the influence of biomass, solar-thermal and small hydraulic power respectively (isolated from the rest of the special regime) on the final electricity prices of the Spanish Pool and the cost of electricity tariffs. Thus, their influence is compared resulting that the economic impact that they have on the system is uneven. For that analysis, artificial intelligence techniques are used to create a descriptive model of the Pool, by means of an ex-post analysis. Algorithms of different typologies are also analysed. Finally, tree models based on algorithm M5P are applied. The main conclusion is that biomass and small hydraulic power have reduced the energy prices of the Pool at 1.48 and 1.45 (sic)/MW h, generating an overall saving for the system of (sic) 50.7 and 200.6 million, and for the average domestic consumer of (sic) 0.12 and 3.01 respectively in 2012. Regarding solar-thermal power, it has reduced the energy prices of the Pool at 1.05 (sic)/MW h, generating an overall cost overrun for the system of (sic) 648.2 million, and for the average domestic consumer of (sic) 12.39. (C) 2014 The Authors. Published by Elsevier Ltd.