Secondary reserve and batteries: how the price varies through the day

Average hourly secondary reserve price from April to August 2026, in euro cents per kW per hour: the upward direction peaks at 17.9 cents at 16:00 and drops to 0.8 cents at 20:00, the downward direction peaks at 4.3 cents at 11:00.

Secondary reserve and batteries: how the price varies through the day

The next instalment of our look at the secondary reserve for sites with batteries. After state of charge, we turn to how the price varies over time.

Behind the meter, the mechanisms compete with one another. The same kW of battery cannot both cut the site’s bill and hold capacity for RTE (the French transmission system operator). The secondary reserve (aFRR) is therefore captured during the hours when the site’s needs are low (because solar already covers them, for example) or cheap to meet.

The secondary reserve pays for two things: capacity held available and energy actually activated. The first accounts for most of the revenue from this mechanism.

Capacity has two prices, one per direction: upward, the battery commits to inject; downward, to absorb.

The upward capacity price peaks in the late afternoon and drops to its floor from 20:00. From April to August 2026, a kW of battery held available earned:

At its highest, at 16:00: 18 cents.
At its lowest, at 20:00: less than one cent.
On average over the day: 4 cents.

The downward price is lower than the upward one and peaks around midday. A kW held available earned:

At its highest, at 11:00: 4 cents.
At its lowest, at 07:00: less than one cent.
On average over the day: 1 cent.

On a site where supply costs per kWh are high, using the battery to save money wins almost all day long. On a site where the supply price is time-varying and cheap in the late afternoon, the balance tips towards the secondary reserve.

One access condition remains: the minimum bid is 1 MW. That means pooling and synchronising dozens or hundreds of batteries under 1 MW.

This barrier is the reason Nexen GridTech exists: we aggregate and control battery installations under 1 MW to open up access to these mechanisms.

Do you develop, distribute or install residential or commercial batteries? Get in touch to explore what the secondary reserve could bring to your projects.