What is the difference between kW and kWh?
Kilowatts (kW) measure power: how much electricity the equipment needs at a moment in time. Kilowatt-hours (kWh) measure energy: how much electricity is consumed or stored over time. A 2 kW load operating for 3 hours uses 6 kWh before system losses.
How do I estimate nominal battery capacity?
For an initial estimate, nominal battery energy = average load × backup hours ÷ usable fraction ÷ inverter efficiency. For example, 2 kW × 3 h ÷ 0.9 ÷ 0.9 is about 7.41 kWh. The 90% values are illustrative assumptions, not CHSHNY product ratings. Starting current, battery power limits, temperature and ageing also affect selection.
Why is this only a starting point?
Actual loads vary. Solar generation may or may not be available during an outage, and the usable fraction must follow the selected battery limits. A qualified designer should check wiring, protection, surge demand and local requirements.