A BESS in France pays grid charges, known as TURPE (tarif d'utilisation des réseaux publics d'électricité), almost exclusively when it imports power from the grid. A 2-hour BESS trading day-ahead pays €5k to €35k per MW per year, depending on the connection voltage. The bill has two parts:

• A power fee on the import capacity in the battery's grid contract. It is a fixed amount per MW, paid whether the battery runs or not.
• An energy fee on every MWh imported. The rate changes by hour and season.

Import fees rise as voltage falls, because a lower-voltage site uses more of the network. At the two lowest voltages, HTA and HTB1, the power fee alone is over 40% of the bill. That raises the question of whether a BESS should contract less import capacity than its rated power.

Key takeaways

• French grid fees fall almost entirely on imports, and get lower as voltage rises: from €35k/MW/yr at HTA (20 kV) to only €5k at HTB3 (400 kV).
• Location matters for network fees: a solar injection zone cuts a BESS's grid bill by 35% (HTB1) to 62% (HTB2), a demand withdrawal zone by 8% (HTB2) to 18% (HTA).
• A 2-hour BESS at HTA or HTB1 that trades only day-ahead saves more in grid fees than it loses in revenue with an import connection smaller than its rated power.
• Optimising dispatch for TURPE adds at most €4.6k/MW/yr because day-ahead prices already point the same way as the tariff.

Should a French BESS contract less import capacity?

TURPE's power fee pushes batteries towards longer durations. It is charged per MW of import capacity, whatever the duration. At HTA, that adds €13.6 to every MWh a 2-hour battery imports at 1.5 cycles a day, against €6.8 for a 4-hour one.

A 2-hour BESS can cut the fee by contracting less import capacity than its rated power. At HTA, cutting import capacity to 50% of rated power loses €4.5k/MW/yr of day-ahead revenue but saves €7.4k in power fees. At HTB1, the best level is 60% in our day-ahead simulation. At HTB2, where the fee is lower, every cut loses money.