Pumped Hydro vs. Batteries

Pumped hydro storage provides roughly 60% of combined pumped-hydro-and-battery grid storage capacity worldwide, about 189 GW. Lithium-ion batteries, after roughly elevenfold growth since 2021, now account for the other 40%, about 124 GW. These technologies do not compete for the same applications; they complement each other across different timescales.

Pumped hydro excels at long-duration, high-capacity storage. A typical facility stores 8-24 hours of energy at gigawatt scale, with round-trip efficiency of 70-85% and a lifespan of 50-100 years. The tradeoff: it requires specific geography (two reservoirs at different elevations), takes 5-15 years to build, and costs $1-3 billion. Lithium-ion batteries excel at short-duration, fast-response applications. A typical grid battery stores 1-4 hours of energy at megawatt to low-gigawatt scale, with 85-90% round-trip efficiency and 10-20 year lifespan. Batteries can be built in months, sited almost anywhere, and respond in milliseconds.

Match to grid needs. Frequency regulation (seconds to minutes): batteries win on response time. Daily solar shifting (4 hours): both can compete. Seasonal storage or multi-day backup (24-72+ hours): pumped hydro is the only proven option at scale.

Compare economics at different durations. At 4 hours, lithium-ion costs roughly $200-300/kWh. Pumped hydro costs vary widely ($150-400/kWh) but amortizes over 50+ years. At 12+ hours, battery costs scale linearly with duration while pumped hydro's marginal cost per additional hour is very low (just more water and reservoir capacity).

Why can't new pumped hydro simply replace all battery deployments?

Geography and speed. Most suitable sites are already developed or face environmental opposition. Permitting and construction take a decade. Batteries can be deployed in months, at any location, for any capacity.

The grid needs both: batteries for fast, flexible, short-duration response and pumped hydro (or alternatives) for long-duration bulk storage.

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