Anything with a motor will get a lot more expensive. AC motors are dirt cheap. Also safety is harder on DC. For one the relays must be made much larger to with

Anything with a motor will get a lot more expensive. AC motors are dirt cheap. Also safety is harder on DC. For one the relays must be made much larger to withstand the nasty arcing. Arc extinguishing is much harder too. Efficiency is a toss up. On one hand, rectifiers are very efficient and you could get by with one rectifier instead of many. On the other, they're not 100% efficient and the voltages are much lower -> more copper. Reliability wont be as good. Rectifiers go all the time (think PC's CPU), there's no comparable failure component in the AC home. Overall the idea has merit, mainly because the most home loads are DC nowadays anyway. But your AC, washer, fridge, garage opener, pool pump, furnace blower, refrigerator, dryer and dishwasher will not be pleased.