Mine is a 422 also. My garage is insulated like a house and has Anderson windows with 3 insulated garage doorsLike this one.
Sure would be nice if all the other products put an hourly usage out like that, makes it easy to quickly calculate a daily cost.
Looks like the Williams models are quite similar.
How much fuel do you use in a yr, do you keep that area at a set temp 24/7, how well is it insulated.
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Here's one on eBay.
https://www.ebay.com/itm/196686127262?_skw=Monitor+Mpi-22+Kerosene+Heater+-+22k+BTU+W/+4+Tanks+Flue+Pipe+Intake+Hose&itmmeta=01JJ50CN7J0AN46BMNPAV9Q3ZW&hash=item2dcb68209e:g:588AAOSwdCpm~Fvv
The 2nd floor is also insulated. I keep it heated at 60 degrees 24/7. In this kind of cold weather it will use almost 3 gallons a day. At 50 it uses around 2 gallons a day. At 20 - 30 degree nights it will use around 2 gallons a day at 60. I have never kept accurate count of gallons a year that I use because I don't care. I'm guessing that in really cold weather that it costs me around $200+ - a month. On Saturday it was 40 out during the day. I filled it up Fruday morning. It used 1.2 gallons in 24 hours. Remember that these are no longer made. Parts are available. The main issue with any of these is keeping the filters clean. Every so often the burner mat needs to be replaced. I have picked up these units for $50 - $150. I'm on my 2nd one now. My first one had electronic issues. The one that I am using now needs a new mat in the burn chamber. I have a spare heater thst has a new mat in the chamber. Sometime soon I willl swap them out and rebuilt the other chamber. Toyo and Rhinnai also made these heaters.