Storage: the batteries that live off the spread

Grid-scale batteries and pumped hydro charge when power is cheap and discharge when it's dear — soaking up the daily price swing the Spread view measures. Here's how that arbitrage works, how fast storage is arriving, and the honest limits. The optimistic counterpart to Dunkelflaute.

A transparent toy battery (1 MW / 2 MWh, 85% round-trip) run over real ENTSO-E day-ahead prices, plus a curated capacity series. The captured figure assumes perfect foresight — an upper bound. Pre-computed and static.

1 · A day in the life of a battery
avg day-ahead price + charge/discharge

The average day-ahead price (line) dips at midday when solar floods the grid and peaks in the evening. A 2-hour battery charges in the cheapest hours (bars below zero) and discharges into the evening peak (bars above) — buy low, sell high.

Upper bound. The captured spread assumes perfect foresight and an 85% round-trip efficiency — the same caveat as the Spread view's arbitrage figure. Real revenue is lower: round-trip losses, cycling wear, and more storage flattening the very spread it feeds on.

2 · Where storage is being built
installed grid-scale battery power · GW

Installed grid-scale battery power has grown roughly tenfold in a few years, led by Great Britain and Germany — the supply-side answer to renewable volatility. Power (GW) is what the market reports track; energy (GWh) differs by each project's duration.

3 · Storage vs the spread
monthly 2-hour spread (TB2) · €/MWh

A battery earns off the gap between the cheapest and dearest hours — the Spread view's TB2. The wider that daily spread, the better the arbitrage case. But the relationship isn't a free lunch: round-trip losses, cycling wear and cannibalisation — more storage flattening the spread as it enters — all pull real revenue below the line.

A battery earns by charging when power is cheap and discharging when it's dear. The figure here assumes perfect foresight and a stated round-trip efficiency, so it's an upper bound on what a real battery captures — the same caveat as the Spread view's arbitrage number. Round-trip losses, cycling wear, and the fact that more storage flattens the very spread it feeds on all pull real revenue below this line.