This reservoir pair stores 2.4 GWh of deliverable electricity (7.9 hours at 300 MW) with a round-trip efficiency of 75.7%, a typical daily-cycling duration. Each cubic metre holds 0.95 kWh, so head matters as much as volume. Arbitrage alone does not cover the levelized cost (119 vs 110 €/MWh); real plants also earn from capacity and grid services.
Energy delivered per full cycle
2.4GWh
3,147 MWh needed to pump it up
Round-trip efficiency
75.7%
generating 87.5% · pumping 86.6%
Discharge time
7.9h
at 300 MW, flow 87 m³/s
Charge time
10.5h
at 300 MW pumping
Gravitational energy (ideal)
2,725MWh
ρ·g·V·H, before losses
Reservoir drawdown
6.3m
1.6% of head; power stays steady below about 15%
Olympic pools
1,000
0.95 kWh per m³ of water
Arbitrage margin / yr
€36,164,992
300 cycles · spread 65 €/MWh
LCOS (incl. charging)
119€/MWh
capital + O&M alone 60 €/MWh
Simple payback
18 yr 11 mo
capex 600 M€
Equivalent battery containers
611
≈3.9 MWh per utility battery container
Real pumped-storage plants for comparison (approximate)
| Plant | Power (MW) | Storage (GWh) | Head (m) | Hours |
|---|---|---|---|---|
| Your design | 300 | 2.38 | 400 | 7.9 |
| Dinorwig, UK | 1,728 | ~9 | ~500 | ~5 |
| Goldisthal, Germany | 1,060 | ~8.5 | ~300 | ~8 |
| Bath County, USA | ~3,000 | ~24 | ~380 | ~8–11 |
| Cruachan, UK | 440 | ~7 | ~365 | ~16 |
- Head varies as the reservoirs fill and empty; this model uses the mean head. Large drawdown relative to head reduces power and efficiency at the end of discharge.
- Evaporation, seepage and environmental flow constraints are ignored. Revenue counts energy arbitrage only; ancillary services (frequency response, inertia, reserve) often earn as much again.