DC optimizers track individual module MPPs and condition DC voltage before it’s sent to a string inverter. They are small units that mount under modules on the PV rack, much like microinverters. Often, they have a safety feature that allows each unit to cut off DC output power to help ensure firefighters or other emergency responders will not be exposed to high-voltage DC wires between the array and DC disconnect. With the use of DC optimizers, unequal numbers of modules in series strings, shading issues, and different module orientations have less of an impact on PV array power production. DC optimizers offer data monitoring options at the module level and many have Web-based interfaces.