Battery Storage

A power electronics device that converts DC (direct current) electricity — from solar panels or batteries — to AC (alternating current) electricity that home circuits use. In a microgrid, inverters are bidirectional: they can also convert AC grid power to DC to charge batteries (operating as a rectifier). Inverter capacity sets the maximum AC output a battery system can deliver. A 10 kW inverter can sustain 10 kW of continuous AC output regardless of how large the battery bank is. Inverter selection is a critical engineering decision — residential microgrids typically use multi-mode inverters capable of grid-tied and off-grid operation simultaneously.

The current energy level of a battery bank expressed as a percentage of total capacity. Example: a 40 kWh battery at 75% SOC holds 30 kWh of usable energy. Microgrid controllers continuously monitor SOC and use it to make operational decisions — when to charge from solar, when to start the generator, and what minimum SOC floor to maintain for emergency reserve.

Two common lithium battery chemistries used in residential storage. Lithium Iron Phosphate (LFP) prioritizes safety, long cycle life (3,000–6,000+ cycles), and thermal stability — better for whole-home applications where longevity and safety are paramount. Nickel Manganese Cobalt (NMC) offers higher energy density (more kWh in less space) but with higher thermal sensitivity. Residential microgrids designed for multi-decade operation typically favor LFP chemistry.