Home Battery Backup, how wire receptacles?

[Nehmo]

Many homeowners, the richer ones anyway, have a backup electrical system to power their essentials in the event of a grid failure. In some areas where outages are common, backup systems are common too. Usually, these systems are natural gas fueled generators that produce 120 volt (in the US) AC to mimic the usual line electricity. Nowaday, considering the dropping cost and according tax credits for solar cell and battery (or just battery) systems, these kinds of systems are becoming more popular. But the wrinkles certainly haven't been ironed out yet.

I would suppose the battery system should supply 120V, and commercial ones go with regular AC. But AC is only necessary in appliances that have transformers. And inverters that convert battery DC to AC are inefficient and suffer from dirty-waveforms. So, maybe 120V DC also should be routed through the house, and DC should be used if possible. If that's the case, then how should it be done? Should there be 2 receptacle outlets everywhere, one for DC and one for AC? Or should there be a switch at every receptacle outlet giving the option? Should DC and AC have different connectors?

This must have already been thought out by several people. Does anybody have any ideas?

Below is an example of a battery home circuit. It doesn't have DC distributed in the house, but it shows the typical elements of such a system.

 

[markz]

Why would you rewire the house for 120Vdc outlets?
Just does not make much sense. I forget what the code book says on that, that too might have to be re-written.
Its updated yearly with a delta beside new code.

Why not then, just use 12Vdc and use all 12V appliances, like an RV.

Then its right back to a regular generator style setup, or solar power setup.

 

[Punx0r]

Many appliances will run on DC (switch-mode power supplies, incandescent lamps, universal motors) but it will burn out switches, thermostats etc due to greater arcing.

 

[Drunkskunk]

AC is safer and more efficient to run through a whole house. it's less prone to arcing, so it can be controlled with a simple wall switch. a 110v 14A DC switch is a beast of a thing compared to an AC switch.

You could run RV appliances on 12v if you wanted, but Low voltage high amperage circuits would lose a lot of power in a house sized circuit. something that is less of a problem of a concern in a small RV meant for occasional use were most of the appliances are within 6 feet of each other and the battery.

Really though, you want a 220v AC system to supply your house. Your house is fed 220 off the line, and it's split by taking one leg to one side of the breaker panel, the other leg to the other side, giving 2 banks of 110v. So if you want to power everything in the house, you'll need to feed 220v AC in.