I would like to install an electric wall mounted garage heater in my 20x30 garage/workshop. It's well insulated and has 240v service. Based on a few online calculators it looks like I will need a unit that puts out about 15-20k BTU. My goal is to take the chill out of the place mostly on weekends, not continuous heating. I live in southern New England. There seems to be a wide assortment of models and brands available. I'm looking for advise or feedback on models, brands, reliability, etc.