For Solis inverters being installed in the United States, a "UL" grid standard is generally appropriate. Examples when searching through the grid standard options are: UL-240V, UL-480V, and UL-600V.
Some areas, like California, would require the California Rule 21 grid standard, which for Solis looks like: R21P3-240, and R21P3-480. There are two versions of each US grid standard, the second version incorporating an "A" for "AFCI" for example: UL-24A, and R21PR-24A.
For systems within the New England ISO [see map below] jurisdiction, an "ISO" grid standard should be selected. Examples for Solis include: ISONE-24A, ISONE-480, ISONE-600.
***The version with "A" in the name must be selected if AFCI is required. Typically, AFCI is required whenever the PV is on a roof, carport, or ground-mount when there is dry grass under the modules.***
Grid standards (codes) in the United States are driven from two different directions. From the top down, the IEEE creates industry standards for interconnection with the electrical grid. The IEEE 1547 standard deals specifically with this very thing. As time goes on, the standard develops as different iterations that typically build on past iterations. From the bottom up, individual ISOs can generate their own set of requirements for DER interconnection with the grid. Common examples of this are California Rule 21, Hawaiian Electric Company Rule 14H, and ISO New England.
The industry typically rolls the requirements from IEEE 1547 with NEC codes into a UL certification. For the US, this is UL 1741. Click here for more information on UL 1741 and Rule 21.
ISOs and RTOs have jurisdiction over large geographical areas of the United States with respect to energy generation, transmission, and power grid regulation. These organizations enforce the rules of interconnecting and interoperating with the grid. Grid codes are known as ‘interconnecting guidelines’. They specify requirements for the technical and operational characteristics of power generation plants, such as wind farms, and for different parties involved in the production, transportation and utilization of electric power. Grid codes address all significant concerns associated with the power grid and guarantee its safe operation and performance. Because utility-scale wind farms can replace conventional power plants, wind farms are expected to support power grids and provide ancillary services similar to conventional power plants.
There are currently seven RTOs or ISOs in the US: