Path-Q Solar
What production estimate should I use when comparing two solar designs?
Answer
Use the same weather basis, site conditions, operating period, and loss assumptions for both designs, and compare monthly and annual kilowatt-hours rather than nameplate capacity alone. Include a conservative case and ensure both estimates are measured at the same point in the system.
Key points
- Compare annual and monthly AC energy production, not just panel wattage or DC capacity.
- Hold shading, soiling, snow, temperature, degradation, outages, and inverter-loss assumptions constant unless the design genuinely changes them.
- Check whether estimates are before or after clipping, system losses, storage losses, or export limits.
- Compare production against the same household load and bill assumptions separately from the production comparison.
What it depends on
- Consistent site and weather inputs
- System orientation, tilt, and shading
- Equipment and inverter configuration
- Whether storage or export constraints are included
Risks and trade-offs
- A larger system may have higher production but lower value for electricity that cannot be used or credited favorably.
- Different modeling conventions can make one design appear better without a real performance advantage.
- A single-point estimate obscures uncertainty and seasonal differences.
Information you may need
- Both designs' full production reports
- Modeling assumptions and loss breakdowns
- Monthly production estimates
- Your hourly or monthly electricity demand and export treatment
Your next step
What to do next
Request normalized comparison reports from both designers using identical assumptions and review the monthly output and conservative case side by side.
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SQ00394