"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.
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.