Path-Q Solar

Can a battery provide backup if the solar panels are on a separate building?

Answer

Possibly, but separate buildings do not automatically share backup. The buildings must have a compatible electrical connection, suitable conductors and protection, and a battery and control system designed to manage the solar source and backup loads together.

Key points

  • The physical location of the panels is less important than how the buildings are electrically connected.
  • The battery may back up only the building or circuits connected to its backup output.
  • Solar on the separate building may not recharge the battery during an outage unless the controls and interconnection support islanded operation.
  • A qualified designer must verify voltage, phase, conductor capacity, disconnects, grounding, and control compatibility.

What it depends on

  • Whether the buildings share an electrical service or have separate services
  • The location of the battery, transfer equipment, and backup loads
  • Interbuilding wiring capacity and protection
  • Compatibility of the inverter, battery, and solar controls

Risks and trade-offs

  • Improperly connecting buildings can create shock, fire, backfeed, or equipment-damage hazards.
  • Long interbuilding runs can add voltage drop and installation cost.
  • A design that backs up one building may leave the other without power.

Information you may need

  • A one-line diagram or description of the electrical connection between buildings
  • Service ratings, distances, and panel locations
  • Solar inverter and battery model information
  • Which circuits must operate during an outage

Your next step

What to do next

Have a qualified electrical designer review the interbuilding connection and confirm whether the proposed battery controls can safely island and serve the intended circuits.

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