BATTERY KNOWLEDGE
How to Choose Energy Storage Battery Capacity
A practical approach to energy, power, runtime, inverter and expansion planning for residential and C&I storage.
Published 2026-08-26Energy and power answer different questions
Battery energy in kWh determines how long loads can run. Inverter or PCS power in kW determines how much load can be supplied at one time.
Start with these inputs
- Critical loads and daily energy consumption
- Continuous and peak power
- Required backup duration
- PV production, grid availability and operating strategy
- Inverter or PCS voltage window and protocol
- Indoor/outdoor environment and expansion plan
A useful proposal separates nominal energy from usable energy and confirms the final battery architecture against the selected inverter or PCS.