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The Toyota Prius. 
Gasoline-electric hybrid vehicles can serve as a UPS (Uninterruptible Power Supply) for your house. 

The Prius, unlike the generator, also has a battery that provides instant, UPS-like power, to your house.  Careful research has shown that most* people would prefer not to go outside to manually pull a cord in the case of a power failure.  The same independent research foundation,** using accepted methods of sampling and polling***, determined that most* people would prefer not to spend money on a big, expensive generator, even if they don't have to pull on the cord.


Cheap pull-cord generator (a few kW) Prius+ 3kW UPS in trunk Expensive generator Prius+UPS in House
Instant ON No - you go outside and start it up No - You must start the car. No.  You wait 10 seconds to a minute Yes
Automatic load
No - you need a long extension cord and plenty of cube taps Yes Yes
Cost $500-$2,000 As low as $200! $5,000-$10,000 $2,000-$4,000
(incremental cost)
Government paperwork None None Electrical and maybe building permit Electrical permit
Grid-related benefits None None Maybe! Maybe!
Fuel Gasoline Gasoline Propane, Natural Gas Gasoline
Noise Is it ever! Just the Prius Probably-depends on model Varies from soft to silent

The "cost" for the Prius, obviously, does not include the cost of the vehicle itself.  If you don't have one and don't plan to get one, "never mind."  If you are thinking of getting one, here's another reason to add to the gasoline-saving and environmental benefits.  If you already have one, well then, it won't cost you anything, will it?

This site is dedicated to the concept of Prius-As-Powerplant. 

***I decided to save money on both because it's so obvious