Path-Q Solar

Can a small business estimate solar savings reliably when its electricity use is tied to unpredictable weather conditions?

Answer

Yes, but not from a single average bill or a simple annual percentage. Use interval or monthly usage data, model weather-sensitive demand and solar production together, and present a range of outcomes rather than one guaranteed savings figure.

Key points

  • Weather can change both the business's electricity demand and the system's solar production, sometimes in opposite directions.
  • Analyze multiple years if available, including unusually hot, cold, cloudy, or storm-affected periods.
  • Separate energy savings from demand charges, fixed charges, export credits, and other bill components.
  • Scenario analysis should include load growth, operating changes, curtailment, equipment outages, and different weather conditions.

What it depends on

  • Interval electricity consumption and billing data
  • Nature of the weather-driven load
  • Solar resource and site conditions
  • Tariff treatment of energy, demand, and exports
  • Expected operating schedule and future load changes

Risks and trade-offs

  • A system sized for rare peak weather demand may be underused in ordinary periods.
  • Annual production estimates can overstate savings if solar generation does not align with load or valuable billing periods.
  • Weather history may not represent future operating conditions.

Information you may need

  • At least one year of interval data, preferably several years
  • Weather variables that drive the load
  • Current bills and rate structure
  • Planned changes to equipment or operating hours
  • Proposed system production model

Your next step

What to do next

Have the proposed system modeled against historical interval load and several weather and operating scenarios, with savings reported as a range and assumptions listed.

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