DC to AC to DC (power tranformers) could be ideal... All you would need is a battery array and converter, plus of course enough photovoltaic's to run it. You know, they have those trickle photovoltaic systems at car stores (Kragen, et al...), and I've seen car battery arrays used this way on "This Old House", etc. It seems the key to me though would be regulation of the output, which would need more than just the converter, but maybe just a regulator like on any audio system would work? You could go with a 240 converter with a step down, which would give you double cycle like many of the larger tube transformers use when they run on 115. I wonder if you had a battery array, maybe six or eight, with trickle photovoltaics, which are about $30. a peice... hmmm... I bet you could get by for under a thousand dollars. But would it work? Plus you could run really super high quality electrical wire after words, for extra bucks.
You should rummage the "Hacking your Prius" internet sites for info - some companies will hack the car for you now, if you don't mind voiding your warranty. Basically the idea is you put eight extra car batteries where your spare tire should go (and move the spare) wired in tandem, and wire it all in to an EV only button, which is dormant in the American model. Then you put a plug-in in the bumper which converts AC to DC and you can go about a hundred miles - so basically you refuel from the grid instead of a gas station; unless you are going on a road trip. I just wish Lotus would come out with a set of ultra-lite parts for the car, or maybe you know, like a cool body style... but the basic idea should be the same for DC home use like you are talking about.