How many kilowatt-hours do energy storage batteries usually store

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.

Similarly, the amount of energy that a battery can store is often referred to in terms of kWh. As a simple example, if a solar system continuously produces 1kW of power for an entire hour, it will have produced 1kWh in total by the end of that hour.

Battery storage duration describes how long the battery can discharge at its rated power. It's calculated: Energy Capacity (MWh) ÷ Power Rating (MW). A 4 MWh battery with a 1 MW power rating has a 4-hour duration. A 1 MWh battery with a 2 MW power rating has a 0.5-hour duration. We've written about storage duration in more detail here.

When manufacturers or installers talk about battery capacity (or energy capacity), they usually talk about one of two metrics a battery is rated on: total capacity and usable capacity. We'll get into why those are different further down. For the time being, it's all just "capacity."

A 4 MWh battery with a 1 MW power rating has a 4-hour duration. A 1 MWh battery with a 2 MW power rating has a 0.5-hour duration. We've written about storage duration in more detail here. C-rate or 'charge rate', is another way of defining how quickly a battery can be charged or discharged relative to its storage capacity.

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.