There have been lots of articles like this one since the winter storms started:

Use a Prius as an Emergency Generator

But they are pretty light on the actual details. These two web sites provide those details:

1) Prius UPS project

2) Priups.com

The first article has a nice diagram that shows you the essence of the idea. A Prius has two batteries: 1) a “normal” 12 volt battery and 2) the “big” 273 volt battery that powers the car’s electric motor. The “normal” 12 volt battery gets its power from a DC-to-DC converter fed by the “big” battery. The big battery gets its power from a generator attached to the engine.

The nice thing about this arrangement is that the Prius will automatically keep the big battery charged by turning on the engine when the big battery needs to be recharged. And the DC-to-DC converter will keep the 12 volt battery charged.

So if you connect a normal 1,000 watt, 120 volt inverter to the “normal” 12 volt battery, then the Prius will provide the inverter with power until it runs out of gas. And it will do it very efficiently.

You can’t pull more than 1,000 watts because that is about the limit of the DC-to-DC converter that is keeping the 12 volt battery charged.

The article shows mounting ideas for the inverter and estimates gas consumption. It looks like a very viable system for powering small appliances, lights, etc. in a house that has lost power from the grid.