Path-Q Solar
How should demand charges be included when calculating commercial solar savings?
Answer
Model demand-charge savings separately from energy savings by analyzing whether solar reduces the utility-defined peak during each applicable billing interval. Annual kilowatt-hours alone cannot establish demand savings.
Key points
- Identify the demand measurement interval, seasonal rules, ratchets, and applicable peak periods.
- Use interval load and modeled solar data to estimate the post-solar billing peak for each period.
- Account for clouds, equipment startup, changing business loads, and peaks outside solar-producing hours.
- Include any export, fixed, minimum, or non-bypassable charges that solar will not reduce.
What it depends on
- Utility tariff and demand definitions
- Interval load data
- Solar output by interval
- Business operating and expansion schedule
- Any battery or load-control strategy
Risks and trade-offs
- A system can generate substantial energy while failing to reduce the monthly demand peak.
- Oversizing solar may not improve demand savings if the peak occurs at another time.
- Battery controls may improve demand reduction but add cost, degradation, and operational complexity.
Information you may need
- Current commercial tariff
- Interval demand history
- Solar production model
- Known operational peaks and future load changes
- Battery or load-management assumptions, if relevant
Your next step
What to do next
Request a bill model that recalculates each historical billing-period peak with the proposed solar output and clearly separates demand savings from energy savings.
Path-Q
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Some details may depend on your location, installer, utility, incentives, regulations, or specific property.
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