Why normalize production by system size
A 10 kW proposal should usually produce more annual energy than an 8 kW proposal simply because it installs more DC capacity. Dividing each installer's first-year kWh forecast by its DC kW makes the underlying production assumption easier to compare.
Why both proposals use the same NREL PVWatts reference here
The comparison intentionally holds ZIP, reference tilt and reference azimuth constant. That isolates differences in the installers' stated production per installed kW. If the real designs use different roof planes or shading, run the single Production Claim Checker separately with the best representative geometry for each proposal.
What to ask when normalized yields differ materially
- Which roof planes and azimuths are included in each design?
- What shading model and shade losses were used?
- What total system-loss percentage is assumed?
- What inverter loading ratio and clipping assumptions are included?
- Which weather dataset and production software produced the forecast?
- Is the stated annual kWh specifically Year 1 production?
Methodology boundary
This is a first-year planning sanity check. It does not select an installer, certify either forecast, model every roof plane or guarantee actual production. Site-specific shade, roof geometry, equipment, clipping, weather, soiling, snow, downtime and installation quality can all move actual output away from a simple shared reference.