Advanced Energy’s (advanced-energy.com) transformerless inverters have a 97% CEC weighted efficiency, and are offered in 3.8, 5.0, 6.0, and 7.0 kW models. All units include an integrated four-string, fused combiner box, as well as AC and DC disconnects. The minimum MPPT voltage varies from 225 VDC for the 3.8 kW unit to 200 VDC for the three larger models; all models have a maximum input voltage of 600 VDC. Data communication is offered as a ZigBee wireless configuration, which is standard for all models. All units are field-configurable for output voltages of 208, 240, or 277 VAC. Inverter weight ranges from 87 to 102 pounds and lifting handles are integrated into the case. Like all transformerless inverters, these units must be installed with ungrounded PV arrays, and installations must meet specific NEC requirements for ungrounded systems (see “Ungrounded PV Systems” in this issue). The inverters come with a 10-year warranty (extendable to 20 years).