BATTERY STORAGE
kWh tells you how much energy a battery can store. kW tells you how quickly it can charge or discharge. A useful design needs both.
kWh: duration
A larger usable energy capacity can carry more solar surplus into the evening or provide more energy through a tariff window. The relevant figure is usable capacity inside the system’s permitted state-of-charge range, not only the headline cell capacity.
kW: rate
Power determines how much of the site load the battery can support at one moment. A battery with plenty of stored energy can still have a relatively modest charge or discharge limit.
Start with the operating objective
Self-consumption, tariff shifting, commercial peak management and resilience are different problems. The load profile, PV surplus, tariff rules, inverter architecture and grid connection should therefore be considered before capacity is selected.
Related: Battery storage systems · Solar PV
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