Have you thought about one of these? Powerpack 600HD http://www.xantrex.com/web/id/182/p/1/pt/29/product.asp It will power a 40W appliance for 7 hours 14W for 15 hours 5W for 56 hours You can pick one up on ebay for under $100 I was thinking about using solar panels to power something and after look...