How to Size a Commercial Battery Energy Storage System (kW vs kWh Explained)

How to size commercial battery energy storage system

How to Size a Commercial Battery Energy Storage System (kW vs kWh Explained)

When planning a C&I energy storage project, one of the most important decisions is sizing. Many clients ask:

  • “How many kWh do I need?”
  • “How many kW should the inverter/PCS be?”

kW vs kWh (Simple Explanation)

  • kW (Power) = how much energy you can supply at one time
  • kWh (Energy) = how long you can supply that power

Example:
A 100kW load running for 2 hours needs 200kWh of energy.

What Determines Battery Size?

Sizing depends on:

  • Critical loads (what must stay on)
  • Backup time required
  • Peak shaving targets
  • Solar PV availability
  • Future expansion plans

Common C&I Sizing Mistakes

Avoid:

  • Oversizing batteries without clear ROI
  • Undersizing PCS/inverter power
  • Ignoring starting currents (motors & pumps)
  • No proper load profiling

A professional assessment ensures your ESS delivers performance and savings.


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