THE SHORT ANSWER
Record the model’s location and weather dataset. A representative long-term resource can support comparison, but it does not predict next year’s clouds or storms.
Find the selected location
Open the model report and record the address or coordinates, weather station or grid cell, and dataset. NREL PVWatts selects solar-resource data as part of its estimate. [1] A proposal for the wrong city or a generic statewide output deserves correction.
Check that the site itself is represented
Weather data describes regional solar resource, while roof direction, tilt, shade and system losses describe the property. Confirm both layers. A nearby dataset cannot compensate for an incorrect west/east orientation or an unmodeled tree.
Understand a typical-year estimate
Historical or representative weather data supports planning across expected conditions; it does not forecast the exact clouds, hurricanes or outages in a future calendar year. Ask how the proposal communicates variability instead of presenting every projected year as certain.
Compare proposals with controlled inputs
When comparing equipment or layouts, use the same location and weather dataset if possible. Otherwise, a production difference may come from the resource file rather than the hardware. Record intentional differences and why the designer chose them.
Archive enough to reproduce the result
Save the model output with location, dataset, array size, orientation, tilt, losses and DC-to-AC assumptions. Date it and connect it to the proposal version. A screenshot of annual kWh without these inputs is not a durable design record.
Before your next conversation
- Record model coordinates or location.
- Identify the weather dataset.
- Check property-specific inputs separately.
- Save a reproducible report.
Primary sources
- National Renewable Energy Laboratory: PVWatts Calculator
Primary source reviewed September 10, 2026. Utility rules, equipment availability, project design and contract terms remain specific to the property and proposal.
Planning examples and questions are Origin’s editorial guidance, not a property-specific diagnosis, engineering design, tax determination or promise of savings. Manufacturer and utility references do not imply an affiliation with Origin.
Make the decision specific to your home.
Review production-model location and inputs with Origin Direct.
Book an Origin Direct review →Scope, pricing and availability are confirmed for your property. A request is not a confirmed appointment.