How to choose home battery capacity

Understand the job of the battery

Most home batteries shift surplus daytime solar into the evening. Other goals can include charging during lower-cost tariff periods or supporting selected circuits during an outage. Backup is not automatic: it requires compatible equipment, a suitable design and a clear decision about which loads need support.

Information needed for sizing

• Typical daily and seasonal electricity consumption.
• Hourly usage patterns, especially evening and overnight demand.
• Existing or proposed solar generation and normal surplus.
• Large loads such as EV charging, air conditioning and pool equipment.
• Whether backup is required and which circuits matter most.

Capacity figures are not all the same

Compare usable capacity rather than relying only on the headline battery size. Also ask about charge and discharge power: capacity indicates how much energy can be stored, while power affects how many appliances the battery can support at once. Warranty conditions, permitted operating range and expected use should be reviewed together.

Compatibility and installation location

A retrofit must be checked against the existing inverter, metering, monitoring and electrical protection. The installer should assess ventilation, temperature, clearances, access, cable routes and manufacturer requirements before choosing a location.