My alternative generator is a Prius as well. I use a Cobra CPI1000 1000W 12V DC to 120V AC Power Inverter with USB Port which I purchased on Amazon for less than $100. In New Jersey during Hurricane Sandy we powered the refrigerator, TV, computers/network, phone chargers and several lamps without getting close to the 1kW maximum. PriusChat is a great forum to get tech details - 1kW is the maximum you should pull from the Prius with an inverter. Beyond that you will likely blow fuses. The attachment is just a couple of alligator clamps onto the small (not the traction) battery posts. I tried to attach a photo, but the File Manager doesn't seem to be working for me..
Sandy had us without power for 12 days. I had a primary gasoline-powered generator that I would crank up periodically to run the well pump (220v). Our water heater is natural gas and we didn't need the furnace (also gas). I have since wired up our furnace with a plug and tested that the Prius inverter will run that as well.
It worked out really well. As Ian points out you can leave the Prius on and it will run the ICE only when the battery level drops. Over the 12 days we only used a couple of gallons of gasoline. The refrigerator is the biggest concern, and with this type of approach you don't have to worry about cycling it on and off. And the noisy generator could then be run intermittently.
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Men have become the tools of their tools.
Henry David Thoreau