From Volume to Value: Renewables Growth, Capture Prices and BESS Opportunities

France's solar and wind fleets have doubled since 2020. The PPE3 trajectories extend that growth to 2035: 55 to 80 GW of solar PV, 35 to 40 GW of onshore wind and around 15 GW of offshore wind, with solar accounting for more than half of the capacity added.

With more solar, more output arrives in the same hours. Production concentrates around midday and lowers the price captured by solar plants.

Since 2023, the price captured by solar has fallen well below the average price, at around half of it in several recent months.

Over the same period, the gap between the most and least expensive hours of the day has widened sharply, especially in spring and summer since 2024. These spreads directly raise the value of an asset that can shift energy from cheap hours to expensive ones.

• Time shift. The battery charges around midday, when solar is abundant and prices are low, and discharges in the morning and evening, raising the average price captured by the PV + BESS pair.
• Portfolio. Forecast errors of renewable assets partly offset each other. A battery covers the remaining imbalance, even when it sits on a different site.
• Shared site. PV and BESS share the grid connection, energy charged directly from the PV pays no TURPE network charges, and the battery can absorb output the connection would otherwise curtail.

Revenues come from a dispatch simulated across Day-Ahead, Intraday, reserves and imbalance with one shared state of charge. Power committed to one market is no longer available to another.

In our case of a 10 MW / 40 MWh battery sharing a site with 10 MWpAC of PV, aFRR capacity is a large part of the revenue stack in the first years. As the BESS fleet grows, reserve markets saturate from the 2030s and value moves to intraday and balancing energy.

Each additional hour of storage adds revenue and cost. The first hours capture the best opportunities and marginal revenue then declines. The optimal duration is the one that maximises net value.