GRID · PUMPED STORAGE
The World’s Water Batteries
The battery layer shows the grid’s faststorage — lithium cells that respond in milliseconds but empty in hours. This layer shows its older, far larger sibling: pumped-storage hydro, the bulk, long-duration half of grid storage and about 90% of the world’s installed storage capacity. The idea is brutally simple — two reservoirs at different heights and a reversible turbine. When power is cheap and plentiful it pumps water uphill; when the grid runs short it lets that water fall back through the turbine to generate. A single plant can bank a small country’s evening peak. They are drawn here as 327 two-reservoir marks, sized by capacity in megawatts: the gigawatt giants anchor the world view, the smaller stations reveal as you zoom. Capacity is mapped on about 88%— the rest draw at the smallest size rather than invent a number. Tap a mark for its name, capacity and country.
From a hillside pond to a continental battery
Pumped-storage plants run from a modest few-hundred-megawatt scheme tucked between two mountain ponds to a grid-scale colossus that can pour out three-plus gigawatts for hours — more than the largest nuclear station. The map sizes every mark by its capacity in megawatts; here is how the mapped fleet divides by scale:
The biggest water batteries
Here the ranking is not just well-mapped — it is broadly true to the real world. Chinaruns the planet’s largest and fastest-growing pumped-storage fleet and tops this list outright: Fengning, the single biggest plant on Earth, can deliver 3.6 GW. Behind it come the long-standing American giants (Bath County, Ludington), more Chinese stations, and Japan’s deep mountain schemes. A handful appear under their native (Chinese or Japanese) name because that is what OSM records. Any capacity tag above 4 GW is clamped so a mis-tag can’t crown the list — though the baked set is in fact clean, topping out at Fengning’s real figure:
Where the plants are mapped
About 55%of the mapped plants sit in Europe — and unlike the other OpenStreetMap layers, that is partly real. The mountainous heart of Europe (the Alps, the Pyrenees, the Welsh and Scottish highlands) pioneered pumped storage decades ago and is dense with it. But it is also partly mapping completeness: Chinaalready operates more pumped-storage capacity than any nation and is building far more, yet shows up at roughly a sixth of the set here. So read it two ways — Europe’s density is genuine andover-counted, while China’s share is understated even as its plants top the size ranking above. The giants are captured everywhere; the long tail still follows where OSM is mapped most fully.
About this data
Every plant comes from OpenStreetMap (power=plant with plant:source=hydro and plant:method=water-pumped-storage, via the Overpass API, ODbL) — the 327 pumped-storage stations OSM knows about. Capacity (the plant:output:electricity tag) is recorded on about 88% of them — cleaner than the battery layer — so capacity sets the size; it’s drawn on a square-root scale and clampedat 4 GW so a single mis-tag can’t paint a monster mark, and plants with no capacity tag draw at the smallest size rather than a fabricated one. Operators are never shown (the no-recon rule). The honest limits: the count leans ~55% Europe by a mix of real density and OSM completeness, and a few of the biggest plants carry only a native (Chinese or Japanese) name — so this is the publicly mapped fleet, not a complete census, even though the record-holders are captured worldwide and correctly ranked. Snapshot taken 2026-06-26.