What is a Solar Witness Test?

You are in the final stretch of your solar project and the solar company informs you they are ready to schedule a witness test. So, what does this mean? The witness test is the final examination and inspection performed by your utility company on your solar energy system to ensure it is safely functioning as expected.

What Is the Purpose of a Solar Witness Test?

The purpose of this test is a form of verification to ensure the system was properly engineered and installed. The witness test examines the operational effectiveness of your solar array when subjected to the anticipated electrical load. Additionally, a visual inspection ensures your array matches the approved design. The test further helps to identify the safe and secure operation and compatibility with adjoining utility equipment.

Does Every Solar Array Get Tested?

Testing depends on the utility company’s solar policy, size and location of the array, equipment selection etc. All utility companies have the opportunity to perform a witness test, however, they may waive the opportunity to conduct one.

When Does the Witness Test Happen?

A witness test will often be scheduled and take place when the solar company has completed the installation and all electrical work on your solar array. Your installer will notify the utility of the completion of the project by submission of a form called the Certificate of Completion (COC). This form is filled out by your solar installer and signed by the owner of the solar array. Once all paperwork is submitted and tests and inspections are completed, the utility will sign off the completion and grant the solar owner Permission to Operate (PTO) the solar array.

How Is the Solar Array Tested?

A utility engineer and representative from the solar company must be present during the witness test. The utility engineer connects a device to the system to measure different strengths of accelerated electrical currents. The primary goal of these tests is to manage the potential impact of the electrical load on the solar array and the utility’s equipment when access energy from the array is sent to the grid. The entire test typically takes about 30 minutes or less. In most applications, there is no power outage or interruption in the electrical service during a witness test. 

What Follows the Test?

Following the completion of the onsite witness test, the utility engineer may leave your solar energy system turned on and operational. In some cases, your utility may choose to review the test findings before officially granting Permission to Operate. Once PTO is received, the array can officially be turned on and begin generating clean, affordable, renewable energy from the sun.