9.0 kWh Home Battery with Backup Power, Three-Phase

Two battery modules of 4.5 kWh under one SMILE-G3-T10 inverter, with the AlphaESS Backup-Box PLUS added. Nine kilowatt-hours of storage and 9.6 kW of charge and discharge power.

Of the four AlphaESS backup power packages, this is the best balanced. Two modules reach almost the full power of the T10, and the Backup-Box can handle 10 kW across three phases. Everything matches up, with no capacity left unused anywhere.

What you can do during an outage

With 9.6 kW available you do not have to be very careful. Lighting, cooling, heating, wifi and a home office keep running without a second thought. A washing machine can join in, a heat pump too in most cases, though you will not want to start both at once. The 9 kWh storage is then the bottleneck sooner than the power: under normal use you get half a day to a full day.

The cabinet has to hang indoors

The Backup-Box PLUS is IP21, so it only suits a dry indoor space. The battery modules are IP65 and can stand outdoors. Those two requirements sometimes clash, because you want the cabinet close to the meter cupboard. Have the installer check beforehand where both will end up.

Handy for maintenance

The cabinet has a bypass switch with a display. That lets an engineer take the system out of the chain without cutting power to the rest of your house. A small luxury, but you notice it the moment something needs attention.

When this is too much

If you have three phases because there was once a workshop, but you now simply use 3,000 kWh a year and your grid never goes down, you are paying €1,250 for a cabinet that gathers dust. The standard 9 kWh package does the same job then.

Installation

Budget an extra €500 for laying the backup circuits.