Someone from a Hydrogen systems Forum came back from a small show by other individuals working on this stuff with an interesting piece of info. There's lots of folks that say "You can't get Free Energy" and then rattle on about their credentials in Thermo Dynamics or science. The folks that are building these Hydrogen On Demand units don't claim that it's free. It costs them a bundle to experiment. What is FREE is the fuel source, and it's everywhere - Air or Water. The rest costs money. How much depends on what you build. Some small and large systems need a lot of maintenance because of the quality of water they use or the types of chemicals they use to get their systems properly 'aged'. A Brew master cleans his beer tanks frequently, but a whisky maker wants the aged flavour from batch to batch. It seems that the Stainless Steel used to make these systems (platinum is too expensive) needs some aging, once in a while. Not a long cleanup job, but it has to be done. Less work than changing oil, more than changing air filters. Probably closer to 20 minutes. Science uses the Metric system, almost exclusively, just so scientists everywhere can use the same info in there studies, research and collaborate, but generally, here in Canada, we consider ONE LITER (LITRE in Canuck) to be a US Quart. The rule of thumb is that for every Horsepower it takes 3 LPM, 3 Litres of of Hydrogen (HH) plus Oxygen (O) electrolysed or separated, per minute. For my 84 HP Six cylinder 200 CID, that would be 252 LPM. That's to run 100% on HydrOxy. It takes a 30 AMP electrolyser on 201 plates of 6" X 6" Stainless Steel (Grade should be at least 304, but 316L non-magnetic Stainless is best, carrying about 4 gallons of water, to run around for about 1,500 miles before filling her up, although you'd check more frequently. That generates 6 to 12 LPM. You could run a decent rider lawnmower on that. Not a car. But you could chop your gasoline bill by up to 30 or 35%. As I get more info, I'll start to build a user-friendly estimating tool. The big thing is that there's enough of these running to even start getting "Rules Of Thumb".