TenneT’s grid charges took half of the revenue of a 2-hour Dutch BESS in the year to September 2026. On a full, firm connection at high voltage (HV), the battery earned €279k/MW/yr and paid €140k of it to TenneT.

The bill is set by what the battery imports. A fixed charge of €66k/MW/yr applies to the import capacity the site contracts. A monthly charge of about €8k/MW applies to the highest weighted import peak. TenneT weights each quarter-hour’s import by when it happens. Import counts in full only on winter weekdays, between 08:00 and 22:00. At noon on a weekday in June, the weight is 0.6.

Contracting less import capacity reduces the bill, but the battery then charges more slowly and earns less. At HV, a 1-hour BESS earns the highest net revenue at 30% to 40% of its rated power, a 2-hour one at 70% to 80%, and a 4-hour one at its full connection.

Every BESS has a higher net revenue with a time-dependent transport right (TDTR) than on a firm connection of any size. TDTR is essentially a flexible grid connection. TenneT drops the contracted charge, and in return it can curtail the site for up to 15% of the year. On a full connection, TDTR adds €28k/MW/yr of net revenue to a 2-hour battery in an area congested by demand, after curtailment.

Key takeaways

• Having a smaller connection costs less revenue because upward aFRR only needs export. Halving a 2-hour BESS’ import connection cuts its upward aFRR capacity revenue by only 5%.
• A longer-duration BESS loses more revenue per MW cut, because each MW of connection has more energy behind it: halving import costs a 1-hour BESS 18% of its revenue, a 4-hour one 28%.
• Time-dependent transport right (TDTR) raises net revenue for every duration, by €23k to €38k/MW/yr at HV on a full connection, because losing the contracted charge saves more than curtailment costs.

Why does a 1-hour BESS gain the most from a smaller connection?

Each 10% cut saves the same amount for every battery, because TenneT charges per MW. What differs for each duration is the lost revenue per MW.

On a firm connection at HV, a 1-hour BESS earns €197k/MW/yr at full import and pays €142k of it to TenneT. At 40% of its rated power, its net revenue rises from €55k to €91k. A 2-hour battery gains only €4k by cutting imports to 80%, and a 4-hour battery earns the highest net revenue at its full connection. At extra-high voltage (EHV), the bill is 23% lower, and only the 1-hour battery is still most economic cutting its import, to 60% of its rated power.