Understanding kW, kWh and Battery Capacity

Kilowatts (kW) describe how fast energy moves. Kilowatt-hours (kWh) describe how much energy you used. A tap and a bucket: kW is the flow rate, kWh is what ended up in the bucket.

Inverters are rated in kW or kVA because their job is to handle flow — the instantaneous demand of everything you switch on at once. Batteries are rated in kWh because their job is volume — how long you can keep going.

This is why a large battery behind a small inverter still trips when the air conditioner starts, and why a large inverter with a small battery runs beautifully for forty minutes and then stops.

Usable capacity matters too. A 5 kWh lithium battery may allow 90% depth of discharge; a tubular bank of the same nominal size may only safely give you half. Compare usable energy, not headline numbers.