A device comprises a platform constructed and arranged to be mounted to one or more solar array modules and one or more solar irradiance sensors on the platform configured to receive incident solar energy, the solar irradiance sensors oriented on the platform so that the received incident solar energy is comparable to that received by the solar array modules, the one or more solar irradiance sensors providing solar irradiance signals in response to the incident solar energy. A processor is on the platform, the processor configured to receive the solar irradiance signals and, in response, generating a performance reference metric based on the solar irradiance signals, the performance reference metric related to the expected performance of the one or more solar array modules to which the platform is mounted. A transmitter is on the platform, the transmitter configured to periodically transmit the performance reference metric to a receiver.