The increasing penetration of grid-connected solar photovoltaics has challenged the existing method of planning and operating the distribution grid. Electric utilities require visibility into the PV installations within their territories and are interested in knowing the operational characteristics of the installed PV systems. This paper provides a novel method to infer the azimuth, tilt, and size of a PV system using only net load data and PV system location. The proposed method is implemented on PV systems in an entire utility district in California, which has both net load and PV production data. System specifications are inferred using the site’s net load data and the accuracy of the inferred system specifications are tested using the site’s PV production data.