The Public Utilities Regulatory Act (PURPA) of 1978 governs small power producers and co-generation facilities—Qualifying Facilities (QFs)—that would interconnect with the transmission grid. “The One-Mile Rule,” promulgated by the Federal Energy Regulatory Commission (FERC) through PURPA, is a regulatory tool to distinguish between what is and what is not a QF. If a facility uses the same kind of generation (e.g. wind, solar, natural gas co-generation) as, has the same ownership as, and is within one mile of another similar facility, then those generators are said to be the same facility. The generation of those facilities is aggregated, and if the total exceeds 80 MW, then the facility is too large to be a QF.
Some Minnesota utilities sometimes misread or misapply this rule to groups of solar installations with the same ownership on the same site, and by that misapplication they attempt to deny net-metering contracts to one or more of those installations. For example, MnSEIA has been presented with situations where the utility misinterprets the One-Mile Rule to read that the aggregate net-metering of multiple meters at a given site cannot exceed 40 kW. This interpretation misreads both the purpose of the federal One-Mile Rule and its appropriate context, which is on the transmission side of substations, within FERC’s jurisdiction.
For a more detailed legal analysis, please see the MnSEIA Legal Memo on the subject. Feel free to show that memo to a utility that seeks to misapply the One-Mile Rule to net-metered solar installations.