18.0 kWh Home Battery with Backup Power, Three-Phase

Four battery modules of 4.5 kWh, one SMILE-G3-T10 inverter and the AlphaESS Backup-Box PLUS. Eighteen kilowatt-hours of storage, 10 kW of power, backup power across three phases.

This is the largest AlphaESS setup we supply as a ready-made system. Want more, then you move to multiple towers or a second inverter, and that becomes custom work.

Storage, not extra power

The C-rate drops to 0.56 here. In practice: the battery can easily deliver more than the inverter lets through, and that 10 kW is the hard limit, even during an outage. What four modules buy you is runtime. Two to three days of base load off-grid is realistic at this size, as long as you are not cooking on induction and running the dryer at the same time.

The cabinet

The Backup-Box PLUS switches 10 kW across three phases, has a bypass and a display, and is IP21. Indoors only, then. With an outdoor battery tower, the cabinet goes in the meter cupboard or the garage, with cabling in between. At this size that is the conversation you want to have up front, because four modules rarely sit indoors.

Space and weight

Four modules plus inverter form a tower of over one and a half metres. Make sure the floor is flat and load-bearing, and keep space free at the front for maintenance. Outdoors is fine, IP65, but do not put it in full afternoon sun against a south-facing wall.

When this is too much

If you use under 4,000 kWh a year, you will never drain this battery, and the 13.5 kWh package is more than enough. Buying bigger than you use does not pay for itself, not even with a dynamic energy contract.

Installation

Budget an extra €500 for the backup circuits, on top of the normal installation package.