I concur, 2.5-3 hours. I like the multiple day cleanings though, working on one this week, finishing tonight. Day one was sealing old panels and installing new, day two will be cleaning years of grease out of around 80' of ductwork and two hoods. This one will have about 12-14 hours when done, but pays almost 3 times per hour the amount of the 2-3 hour jobs.