The tank holds 5L, which is roughly 1.25gal. I can run the 8KW heaters for ~12 hours on that. The claimed burn rate is .35l/hr but it depends on the settings.
For all the different ones I've had, the admin password is "1688". So if you have that you can adjust it more.
I run it off a 12v power brick used for LED lighting. When the igniter first turns on it uses enough current to pull the regulator down to 10.9v. I have the heat discharge through a toilet flange in the wall of my garage. The heater is outside of the garage. It would be more efficient if I was using garage air to heat, but I like the idea of fresh and dry air getting pumped into the garage. I have a piece of 10' long exhaust pipe on it to get all the combustion fumes a ways away.
I have a second one (and third one that is different than the other two) that I'm going to set up to see if I just run two for like an hour then switch to one I can get the heat up faster. I've been running one from 7or 9am until I go in for the night sometime around 9-10:30pm.
My long term goal is to get the garage so by night time it's in the upper 40s and in the morning it never gets cold enough to freeze.
I have a giant torpedo heater and it will roast you out in minutes, but it not only eats all the oxygen it makes the garage so wet it's crazy. There will be frost on the inside of the walls and the garage doors will get so heavy the opener struggles. Usually what I do with that is leave it running blowing in through the service door. At the end of the day when I'm done I open both garage doors for a few minutes to let the moist air out then close. So far I haven't used the torpedo heater yet.