Giving it a star ratting is a little difficult. As far as the AC function is concerned, it does very well for a single room. Haven’t tested it for a larger area but confident it’ll be sufficient. For heat, I’ve read from the qa that it can heat up to a 20x20 garage. I have a slightly larger garage about 22x22 size garage. The heater didn’t even take the edge off for a winter night (40 degrees). Unless your garage is fully insulated or half the size, I don’t see it doing much of anything. Also, yes you need to vent for the heater function. It blows out cold air from the exhaust hose so make it go outside or something.