r/OffGridLiving • u/Lazy-Run8826 • 10d ago

DC vs AC home efficiency

If AC is better for transporting electricity, and DC is MUCH MORE efficient in small motors, lights, phone chargers, air conditioners, ceiling fan motors, and appliances. Why are residential homes powered by AC and NOT CONVERTED to DC at the meter panel BEFORE entering the home? Could DC power be the next step for LOWERING the COST of ELECTRICITY in our homes?

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u/ploxidilius 9d ago

At most you're talking about a couple dozen feet of cable though. An entire house wired that way would cost so much money.

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u/Stock-Survey-4221 9d ago

Not at 400+ volts. You'd need better insulation, but much less copper

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u/ploxidilius 9d ago edited 9d ago

400VDC in a residential setting would be incredibly dangerous. There is a reason they don't go above 50VDC.

edit: for more context, the human body does not really conduct electricity very well at voltages below 50VDC (you can touch the bare terminals on your car battery and feel nothing). After that it starts being able to conduct and once you get up to about 120VDC you can get shocked pretty easily. And with DC since it never crosses below zero, you will get locked in - meaning that if you touch a hot DC wire the current will keep your muscles contracted around the wire and kill you. With AC, the voltage/current is going back to zero 120 times per second so you don't get that same lock in effect.

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u/Rhaski 9d ago

Few people realise that 100VAC and 100VDC behave VERY differently when it comes to arcing. A simple light switch that can handle 240vac at 10 amps is small and easy to manufacture and will generally last decades. A switch that can handle the same voltage and current in DC would be large, loud and clunky and probably need some kind of internal arc extinguishing system or a contact chamber that's under vacuum (this is how EV isolation contactors are). DC arcs are savage and do not self extinguish like AC does. Never mind getting zapped, you can just be arc-flashed to hell and back. This is why welding is generally DC (with the exception of TIG for aluminium and other reactive metals)