Path-Q Solar

How should I size the solar array to recharge a battery within my target recovery time after an outage while also powering essential loads?

Answer

Estimate the battery energy that must be replaced, add the energy used by essential loads during the recharge period, account for charging and system losses, and divide by the expected solar production during the available recovery window. The array must also be compatible with the inverter's charging and input limits.

Key points

  • The energy target includes both battery replenishment and concurrent essential-load consumption.
  • Use production expected during the relevant season and weather conditions, not only ideal rated output.
  • A shorter recovery time requires more array capacity or reduced loads.
  • Battery and inverter power limits can constrain charging even when the array is larger.

What it depends on

  • Battery energy removed during the outage
  • Target recovery time and available sunlight
  • Essential-load energy and peak power
  • Charging efficiency and inverter input limits

Risks and trade-offs

  • Sizing from average annual sunlight may understate recovery time during poor-weather periods.
  • A larger array may be unable to charge faster if the battery or inverter limits charging power.
  • Prioritizing rapid recovery can increase equipment cost and may require load shedding.

Information you may need

  • Battery usable capacity and state of charge after the outage
  • Essential-load energy and peak demand
  • Target recovery duration and season
  • Array, inverter, and battery charging specifications

Your next step

What to do next

Ask for a seasonal recovery simulation showing array output, essential-load consumption, charging losses, and expected time to restore the target battery reserve.

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SQ00707