The majority of devices might be USB powered, but the majority of energy use is from large AC appliances. USB is solved by adapter or special outlets. Also, th

The majority of devices might be USB powered, but the majority of energy use is from large AC appliances. USB is solved by adapter or special outlets. Also, the DC voltage for house wires and batteries need to be much higher than USB voltage so will need conversion. Might as well have it be AC to DC converter. There is a problem connecting solar panels to batteries and needing two inverters. But that could be solved with higher voltage DC between them.