How big a battery is usually used for energy storage

Battery energy storage capacity is the total amount of energy the battery can store, measured in kilowatt-hours (kWh) or megawatt-hours (MWh). Think of this as like the size of a water tank where you measure the water capacity in litres.

Battery capacity is the amount of energy a battery can store, typically measured in ampere-hours (Ah) or watt-hours (Wh). Ampere-hours indicate the total charge a battery can deliver at a specific current over time, while watt-hours provide insight into the energy stored, factoring in voltage.

Learn what determines battery size, including energy storage capacity (kWh), power rating (kW), charge rate (C-rate), storage duration, and energy density. Understand how these factors impact performance in energy storage systems.

Batteries are rated for two different capacity metrics: total and usable. Because usable capacity is most relevant to the amount of energy you'll get from a battery, we like to use usable capacity as the main "capacity" metric to compare storage products. Also, from our energy storage glossary, see how the two terms differ below:

Battery “size” also needs to be understood over time—how much energy the battery can deliver across its usable life. This is often described as lifetime energy throughput, measured in total MWh, or in terms of some number of full charge and discharge cycles.

From lithium-ion batteries and modules to power ratings, capacity, and certifications, each specification plays a vital role in determining the performance and suitability of a battery storage system for your specific needs.