According to Wikipedia:
solar panels produce voltages around 30 V. This is too low to be effectively converted into AC to feed to the power grid. To address this, panels are strung together in series to increase the voltage to something more appropriate for the inverter being used, typically about 600 V.
A power optimizer on each panel would then ensure the failure of one panel won't ruin the overall production of the serial circuit of panels, and roughly 600V would be delivered off of the roof to a single inverter.
Microinverters, on the other hand, do not spit out 600V from a serially connected loop. They convert to 120VAC directly at each panel from the ~30VDC output at the panel. These microinverters are more expensive than power optimizers, for obvious reasons, but are touted as being more efficient.
- The wikipedia article says it's more efficient to convert to residential AC from 600VDC than from 30VDC
- Industry says the most efficient system is micro inverters, which converts to 120VAC from 30VDC
How can microinverters be more efficient than power optimizers if the most efficient way to convert to residential AC is from 600VDC?