A 2-hour BESS with a full grid connection in the Netherlands earned €303k/MW/yr over the first nine months of 2026.

Each additional hour of duration adds less revenue than the one before. Going from 1 to 2 hours adds the most, €88k/MW/yr, because it opens up aFRR capacity, the largest revenue stream of a 2-hour battery. A 1-hour battery has too little stored energy to guarantee its aFRR obligation.

Beyond 2 hours, the extra duration goes into day-ahead trading instead. A longer battery captures more value in each cycle, so a MW used for trading comes close to what the same MW earns held in aFRR capacity.

Key takeaways

• Adding duration pays less with every hour, from €88k/MW/yr going from 1 to 2 hours down to €17k going from 3 to 4 hours, so revenue per MWh of BESS capacity falls from €215k to €87k.
• Wholesale trading revenue is rising for 4-hour batteries because higher gas prices widened day-ahead spreads from March 2026. Day-ahead paid a 4-hour battery €77k/MW/yr in 2026, against €19k across 2025.
• Without ancillary services, a 4-hour battery keeps 53% of its 2026 revenue, against 38% for a 2-hour one, because more of its revenue comes from wholesale trading.

Why does each additional BESS duration increase pay less?

Going from 1 to 2 hours more than doubles the aFRR capacity a battery can sell: on average 4.8 MW on a 10 MW / 2-hour battery, against 2.2 MW on a 1-hour battery. aFRR capacity is paid per MW, but every MW has to be backed by energy in the battery. For shorter durations, the benchmark reduces the aFRR capacity a battery can sell. Every MW of upward aFRR needs enough charge to deliver, and every MW of downward aFRR needs enough empty space to absorb.