1.6.1 The basics

Battery capacity is measured in kWh (energy), not kW (power). A 15 kWh battery can typically run an average household for 10–15 hours.
99% of residential batteries today are LFP (lithium iron phosphate) — safer than NMC, longer cycle life (6,000+ cycles), 10–15 year service life. The fire risk is lower than the phone in your hand.
Key specs to read: Usable Capacity, Continuous Power (kW), Peak Power, Cycle Life, Depth of Discharge (DoD).