look up how much horsepower a stanley steamer made. If you think you can make enough electricity for a whole house with a lawnmower engine, THINK AGAIN buddy boy.
According to Google.....the equivalent of 15KW. And not precisely "garage-sized". Now.....add the technology advances demonstrated for the prototype steam cars from the 1970's, and I think you'll find you CAN power your house with a system "slightly" smaller than "garage sized".
The E-cat of the 6 October demonstration is rated 27KW. As run, it was throttled WAY back (only one "core" of three being run).