The problem with the whole house DC UPS is the voltage drop associated with distributing power at low voltages. For example: 100 watts of power at 100 volts (just to pick a round number somewhere near the actual line voltage) requires a current of 1 amp. If the wire from the power source has a resistance of 1 ohm, there's a drop of 1 volt, which is insignificant. If we supply 100 watts of power at 10 volts, the current is now 10 amps and the same 1 ohm of resistance has a drop of 10 volts, which is all we started out with! For the loss to be the same percentage as it was at 100 volts, the wire now needs a resistance of 0.01 ohm. Decreasing the resistance from 1 ohm to 0.01 ohm requires a wire with 100x the cross sectional area, or 10x the diameter.
(this is why the power company distributes power at high voltage and steps it down when it gets near your house)
Now, a PC power supply with batteries built in might make some sense.
"Now, a PC power supply with batteries built in might make some sense."
Have seen ads for such a thing, although not in many years. Always struck me as a good idea.
"...a house UPS that ducks the inefficiency of the inverter by just feeding DC directly to all devices that are just going to rectify the AC anyhow."
There do exist whole house UPSes... but they immediately step the battery voltage up to 120VAC before distribution. Thing is, with modern inverters, there just isn't that much inefficiency (yay cheap microcontrollers); a few percent, usually.
Ohm's Law
(this is why the power company distributes power at high voltage and steps it down when it gets near your house)
Now, a PC power supply with batteries built in might make some sense.
Re: Ohm's Law
Have seen ads for such a thing, although not in many years. Always struck me as a good idea.
"...a house UPS that ducks the inefficiency of the inverter by just feeding DC directly to all devices that are just going to rectify the AC anyhow."
There do exist whole house UPSes... but they immediately step the battery voltage up to 120VAC before distribution. Thing is, with modern inverters, there just isn't that much inefficiency (yay cheap microcontrollers); a few percent, usually.