Connecting your PV system to the utility grid

connecting to power gridThe majority of U.S. residential and commercial PV systems are grid-interactive, otherwise known as grid-tied, which means that they are designed to be able to export excess power to the utility grid. Export occurs when the power generated by the solar panel system is greater than the power used by the loads onsite.

A photovoltaic system will be given permission to interact with the power grid only after a formal approval has been issued by the utility company. The process through which a utility verifies a solar system’s compliance to its technical and administrative requirements is commonly referred to as the interconnection process.

The interconnection process runs in parallel with the permitting process. During this process, the local Authority Having Jurisdiction (AHJ) verifies the system’s compliance to the National Electrical code, fire code, and other local standards. While the AHJ and the utility company will generally not interact during the process, they will require and recognize each other’s approval documents.

During the interconnection process, utilities certify that a PV system meets the following general requirements:

  1. The power exported to the grid is measurable and compliant with the grid’s standards in terms of voltage, frequency, power, quality, and that the equipment used is certified.
  2. The AC side of the PV system (between the inverter and the utility meter) meets the utility’s safety requirements (labelling, location of equipment, and connection to electric panel).
  3. The power and energy generated meet the net metering program requirements.

To gather the necessary information about the proposed system, utilities usually require that an interconnection application is submitted to their interconnection department. The application may be submitted by the account holder or, when properly designated, by the contractor that designs and installs the PV system. The interconnection application usually includes professional technical drawings, such as a site plan and an electrical diagram.

In the parallel permitting process, the AHJ will complete the inspection and, when passed, will issue a signed final permit.

Once the utility has received the approved final permit, it will schedule an inspection of the installed system. During the site visit, performed by qualified utility personnel, the solar system will be tested and, if necessary, revenue meters installed and/or replaced. When the system is approved, the utility will notify the account holder and the installer, who will then be able to turn on the system and export power to the utility grid.

Connection to the main panel

utility connection Grid interactive systems have a physical connection to the existing electrical equipment, which is electrically continuous with the power grid. The technical requirements for interconnecting a customer-owned generator are listed in a technical document (usually called Electrical Service Requirements) that is published by the utility company.

So that is a simple explanation of what is involved in the PV interconnection process. If all this seems overwhelming, have no fear. At NC Solar Now, we take care of all the paperwork and permitting process. We will keep you informed along the way.

Image courtesy of Home Power Magazine