THE SHORT ANSWER
A dip in a solar curve is not a component diagnosis. Compare repeated patterns, weather, shade and device status across several suitable days.
Name the curve correctly
Record whether the graph shows power or energy and the interval size. Power can change quickly; daily energy accumulates. Save the complete day rather than a cropped dip so sunrise, peak and afternoon recovery remain visible.
Compare repetition
Check several clear days and several cloudy days. A consistent dip at the same solar time suggests a different question than irregular cloud-driven variation. NREL’s PVWatts demonstrates that orientation, losses and weather shape expected production. [1] It is an estimate, not a fault detector.
Look across devices
If owner monitoring supports device detail, compare adjacent modules and roof planes. Capture alerts and missing data. Uniform flat-topping, one-device loss and a whole-system drop require different tests; none should be labeled from the graph alone.
Inspect the environment safely
Use ground photographs to record trees, vents, new construction, debris or a changed roof feature near the affected plane. Do not climb onto tile or wet roofing. DOE maintenance guidance combines monitoring with qualified inspection and corrective work. [2]
Ask for a written conclusion
A service report should state the data reviewed, field tests, observed cause and whether work is recommended. If the curve is normal for the design, keep that explanation with the original proposal. If repaired, save before-and-after comparable days.
Before your next conversation
- Save full-day power and energy views.
- Compare repeated clear-day timing.
- Capture device-level patterns and alerts.
- Document nearby shade from the ground.
Primary sources
- National Renewable Energy Laboratory: PVWatts Calculator
Primary source reviewed September 10, 2026. A field diagnosis, warranty decision, permit or utility action remains specific to the installed system and property.
- U.S. Department of Energy FEMP: Operations and Maintenance for Solar Photovoltaic Systems
Primary source reviewed September 10, 2026. A field diagnosis, warranty decision, permit or utility action remains specific to the installed system and property.
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.
Need help with the system you already have?
Request solar maintenance when a repeatable dip remains unexplained.
Request solar service →Equipment support, diagnostic fees, availability and accepted work are confirmed before service. A request is not a confirmed appointment.