Path-Q Solar

What electricity data should a business use to estimate a department's load for solar sizing when it has no separate meter?

Answer

Use whole-site interval consumption as the starting point, then allocate the department's load using submetering, equipment ratings and operating schedules, temporary measurement, and production records. Do not treat a simple floor-area or headcount allocation as a reliable solar-sizing load without validation.

Key points

  • Collect at least a year of bills and, if available, 15-minute or hourly interval data.
  • Inventory department equipment, demand ratings, operating hours, seasonal schedules, and process changes.
  • Use temporary submeters or circuit-level measurements where the department's circuits can be isolated.
  • Separate the department's coincident peak demand from its annual energy use.

What it depends on

  • Availability and resolution of utility interval data
  • Whether department circuits can be isolated or measured
  • Operating schedules, production volume, and shared equipment
  • The intended allocation method and solar design objective

Risks and trade-offs

  • Allocation from whole-site data can misstate the department's load when departments operate at different times.
  • Equipment nameplate ratings usually overstate actual energy use but may help identify peak-demand risk.
  • A department-only estimate may not match the site's tariff, demand charges, or interconnection constraints.

Information you may need

  • Utility bills and interval data
  • Panel schedules and electrical drawings
  • Equipment inventory and operating schedules
  • Production or occupancy data for the same periods

Your next step

What to do next

Ask an energy professional to create a department load estimate using interval data and temporary measurements, and document the allocation assumptions before sizing solar.

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