Path-Q Solar

Should I size a battery's energy capacity based on my typical nightly use and its power rating based on my peak evening demand?

Answer

Yes, as a starting principle: energy capacity addresses how long loads run, while power rating addresses simultaneous demand and startup surges; both should include system limits and reserves.

Key points

  • Peak demand and motor starting currents can exceed average use.
  • Usable kWh is reduced by reserve and conversion losses.
  • Battery power must be compatible with the inverter and backup panel.

What it depends on

  • Hourly and instantaneous loads
  • Appliance startup behavior
  • Backup configuration

Risks and trade-offs

  • High kW without enough kWh gives short runtime.
  • High kWh without sufficient kW cannot run simultaneous loads.

Information you may need

  • Load list and runtimes
  • Peak and surge demand
  • Battery usable kWh and continuous/surge kW

Your next step

What to do next

Prepare a load schedule identifying essential loads, simultaneous operation, and motor surges.

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SQ00049