The alarm cleared.
Now verify the repair.

Agree on acceptance before the work starts

A repair scope should say what will count as completion. That may include required electrical or mechanical checks, restored protection and communications, operating verification, and a defined follow-up window. Agree on the evidence while the failure is still documented, not after the contractor has left.

DOE FEMP's O&M guidance expressly includes procedures for reacceptance testing after repair. The specific tests must come from the equipment instructions, site procedures, engineering requirements, and the actual defect. A generic checklist cannot substitute for those requirements.

Use three separate acceptance questions

Was the defect addressed? The work order should identify the confirmed cause, affected equipment, parts or settings changed, and the required verification. When the cause remains unconfirmed, say so. Replacing a part and observing a temporary restart is not the same as demonstrating why it failed.

Is the equipment operating as intended? Review status, alarms, relevant measurements, protection behavior, communications, and any operating restrictions. An inverter may be online while one input remains unavailable. A monitoring portal may report fresh data without proving that the production meter is correct.

Did the expected energy reach the measurement boundary? Define whether recovery is measured at an inverter, a production meter, or another agreed point. State the observation window and any controls or downstream limitations. Keep these three conclusions separate in the report.

Make a fair before-and-after comparison

Solar production changes with weather, temperature, time of year, shading, and operating availability. Comparing yesterday's energy with today's energy can therefore misstate repair benefit. Use a suitable weather-adjusted model or comparable equipment, and document why the reference is appropriate.

DOE FEMP recommends monitoring actual output against expected performance. For a repair comparison, keep timestamps, interval lengths, sensor sources, and data-quality exclusions consistent. Record other interventions such as cleaning, changed control settings, or restored monitoring so their effects are not attributed to the repair by default.

Do not combine model-based performance indices with differently defined contractual performance ratios without explaining the calculation. TerraSun's performance-ratio and availability guide provides a starting point for agreeing on the metric.

Separate measured recovery from a forecast

Measured recovery describes an observed period with an identified comparison basis. An annual projection extends beyond that period and adds assumptions about future weather, availability, degradation, recurrence, and controls. Label it as a forecast and retain the assumptions.

Illustrative example: a repaired block records 5,700 kWh during a review window for which the agreed model predicts 6,000 kWh under the measured conditions. That is 95% of that modeled reference. It is not, on its own, proof of the repair's incremental benefit: the pre-repair comparable result and other changes are still needed. Neither figure establishes a contractual acceptance threshold.

Similarly, a 50 kW nameplate rating does not mean that a repaired inverter recovers 50 kWh every hour. The available resource, system design, and actual operating window matter.

Keep a complete but usable evidence package

• Original complaint, fault chronology, equipment identifiers, and diagnostic findings.
• Approved repair scope, work performed, parts and settings changed, and updated records.
• Required inspection or test results and the personnel responsible for acceptance.
• Operating data, measurement boundary, comparison method, exclusions, and uncertainty.
• Open defects, isolated circuits, parts on order, warranty actions, and operating restrictions.
• Follow-up responsibilities, review date, and the evidence that would trigger a return visit.

Preserve the distinction between completed work and unresolved work. A single site-wide status of operational can hide an intentionally isolated string or a deferred component. Link the closeout to the owner's asset-management record, not only to an invoice.

Use follow-up monitoring as verification, not a guarantee

Choose a follow-up window suited to the defect. A temperature-related issue needs suitable operating conditions; a weather-correlated alarm may not recur during a dry visit. Record the limits of the observation rather than claiming an intermittent problem can never return.

TerraSun's repair service and monitoring support can be scoped around these acceptance questions. Send the prior work order, alarm history, and production data. Any electrical or mechanical re-testing remains the responsibility of qualified personnel working under the approved site procedures.

Technical references

• DOE FEMP: Reacceptance testing and maintenance records
• DOE FEMP: Monitoring and expected performance
• OSHA: Solar electrical hazards