Backup / Protected Loads Panel

Updated 2026-08-24 · Read this page as Markdown

A separate distribution board containing the circuits that a hybrid or off-grid inverter will keep supplied during a grid outage. Only the loads wired into this board stay live when the utility supply fails.

The panel exists because a battery inverter's backup output is normally rated well below the whole-house load, so the circuits worth keeping — lighting, refrigeration, communications, heating controls, a few sockets — are separated out and everything else is left on the main board. Getting the selection right at design time is important, since rewiring circuits afterwards is disruptive. Two things to check: the surge capability against motor loads such as a fridge compressor or a well pump, and the transition time, since a break of even a fraction of a second will reset computers unless the system offers a genuinely uninterruptible changeover.

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Related terms

AC Coupling A storage architecture in which the PV inverter and the battery inverter are separate units connected on the AC side. Solar energy is converted to AC first, and any surplus is then converted back to DC to charge the battery. DC Coupling A storage architecture in which the PV array and the battery share the same DC bus inside a single hybrid inverter, so solar energy charges the battery without first being converted to AC. Only the energy actually consumed or exported passes through the DC-to-AC stage. Round-Trip Efficiency The proportion of energy put into a battery system that comes back out again, after accounting for losses in charging, storage and discharging. A round-trip efficiency of 90% means ten kilowatt-hours in returns nine.

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