With an increasing share of renewable energy generation, the evolution of reserve needs may represent an important challenge for the power system. The evolution of reserve capacity needs in this context has been studied extensively in the literature (Hirth & Ziegenhagen, 2015). On the contrary, reserve energy needs have been little studied. This work focuses on analysing the relationship between reserve energy demand and load, wind, and solar generation. To that end, autoregressive models with exogenous variables are estimated for 2019 French data. We find a positive impact of renewable energy generation on downward aFRR energy demand and a negative impact on upward aFRR. These results can be interpreted as the influence of the number of bids in the intraday market on the level of forecast errors that are balanced in this market and does not contribute to the imbalance of the system