Until recently, it was difficult to pinpoint individual modules in an array that produced less than their rated output. Array-level monitoring reports output data only in total kilowatts (and/or kWh) by the inverter display or a separate production meter. But module-level optimization and monitoring (such as from EiQ, Enphase, Exeltech, Solar Edge, or Tigo Energy products) can allow installers and homeowners to track the output of individual modules.
Without module-level data, identifying low-producing modules in residential-sized arrays, which commonly have at least 10 modules, can be difficult, since a 10% or 20% reduction in output from a single module only results in a small reduction in total output. (In a 10-module system, for example, you’ll only see an overall performance loss of 1% or 2%.) Module-level monitoring allows system owners to compare each module with others in the array, and underperforming modules become easy to spot.