Do the math, I found the honda 5hp one at northerntool to be about the most efficient math wise compared to the kubato diesel generator. I think I have that name right. Of course the diesel could be run on biofuel if it checks out as that can degrade the hoses and tank. Once its warmed up it could run on raw filtered vegetable oil.
Maybe one day we will have have an old prius laying around we can use as a back up power supply?