The genny shouldn't cost much in the way of fuel as long as you use it sensibly - i.e. when it is delivering less than 750W or so, turn it off. The amount of fuel it uses is pretty constant per hp-hr though the efficiency falls off badly at less than 10% or greater than 70% rated load. A diesel genny will cost less to run than a portable Honda, in fuel. You will need to service it, of course, but then you have to service the Honda and you have a bigger, better and more convenient generator.