DE

Knowledge

What a storage unit would have earned on a real day.

Set power, storage duration and operating mode, pick a day, drag the windows. The calculation uses the published prices of five real days — with round-trip losses, with open assumptions and without any promise of return.

Five real days, not a forecast.1 What a storage unit will earn depends on how many others do the same: every unit that connects narrows the Spread it lives on.

The calculator needs JavaScript. The curve shows the day-ahead price of the first day; the assumptions below apply unchanged.

Price curve of the selected day with the charging and discharging windows of the configured storage unitDay-ahead prices on 5 September 2025, Germany/Luxembourg bidding zone, hourly values. A trading day without anything unusual: shallow midday dip, early-evening peak, no negative hour. Charging 12:00–16:00 at an average of 75 euros per megawatt hour, discharging 18:00–22:00 at 133 euros. Below, the state of charge from zero to one hundred per cent.
Power at the grid connection point
10 MW
Storage duration
Operating mode
Day

Revenue on this day

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Across the five days in this selection
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Arithmetically, at 365 days like this one
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A year is not 365 identical days. The line above shows how far apart the days in this selection are.
Full cycles per day
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Capacity
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Price range of the day
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Every assumption, in the open
Data
Hourly values of the day-ahead auction in the Germany/Luxembourg bidding zone, published by the Bundesnetzagentur.1 Five selected days between September 2025 and September 2026, taken unchanged.
Efficiency
85 per cent round-trip, charged entirely to the discharge side: one hour of charging draws 1 MWh per MW from the grid, one hour of discharging returns 0.85 MWh per MW.
Capacity and cycles
Capacity is power times storage duration. The state of charge stays between 0 and 100 per cent, and no cycle draws more than the capacity — that is this calculator's cycle limit. What a manufacturer's warranty permits is in their contract, not here.
Contiguous windows
The calculation uses contiguous windows, because those can be dragged in the chart. A free choice of hours earns more on some days; how much is shown below.
One cycle
One charging window, then one discharging window, each spanning the storage duration at full power.
Two cycles
Two pairs in sequence. Twice the throughput means twice the wear on the cells; if the second cycle does not pay, it is not run.
Grid-friendly
The same energy over twice the time at half the power. That halves the load at the grid connection point and captures less Spread — a unit that helps the grid more than its own revenue line.
Negative prices
With negative prices the arithmetic inverts: offtake is paid for, feed-in costs money. Because only 85 per cent comes back, the loss then earns. That is not an error in the calculation, that is the market.
One market only
Only the day-ahead market is calculated. In practice a storage unit trades several markets at once — intraday, balancing, capacity. The day-ahead revenue is therefore a floor, not the result.
Not included
What is calculated is the day-ahead revenue, nothing else. Not included:
  • grid fees, levies, taxes
  • marketing costs and availability
  • cell degradation
  • investment, financing, operation
No return figure
This calculator states revenues. A return requires capital expenditure, financing and operating costs; it does not know them and therefore does not compute them. Anyone who needs a defensible figure needs a project and a conversation.

Why this calculator shows less than is possible

A storage unit that works the day-ahead market alone leaves money on the table. In practice it is traded in parallel: intraday, balancing reserve, capacity products. Taken together, the figure is higher than the one shown here.

We show it alone anyway, for one reason: the day-ahead price is the only revenue that is published in full for every day and that you can verify yourself.1 Everything else we would have to assert.

The other direction belongs to the picture: the gap between the cheapest and the dearest price of a day is the basis of this business, and it narrows as more storage enters the market. In 2025 grid connection requests for around 574 GW were filed.2 Not all of them will be built — but anyone who calculates with today's spreads is calculating too high.

Two ways on from here

You own land.

Whether a storage unit is possible on your plot depends not on revenue but on the grid connection nearby. We will tell you what can come of it — including when the answer is nothing.

Offer land

You assess projects.

A defensible revenue case needs load profiles, grid fees, offtake contracts and the dispatch of the specific site. We calculate that per project, not in a browser.

For institutional investors

Sources

Sources last reconciled on

  1. Bundesnetzagentur | SMARD.de: Day-ahead wholesale prices, bidding zone DE-LU, hourly and quarter-hour resolution (licence CC BY 4.0). As of 2026-09-12. Go to source
  2. Bundesnetzagentur (Monitoring), berichtet von pv magazine: Grid connection requests and offers for battery storage in 2025. As of 2026-08-25. Go to source

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