I'm shopping for a small, portable space heater to bring some warmth to my barely-1-car-garage which is our "shop" and storage area for bikes. My use would be: flip it on, let the place warm up, go out and do some projects, shut it off and unplug.

I found this, which gets some good reviews on shop websites. Specs say it has a 120v plug and draws 15 amps.

It's out of stock at the manufacturer but available on Amazon. The Amazon reviews, however, complain that it needs 220v and 30 amps or it will trip the circuit breaker. Realizing that the Amazon reviews might apply to a different product, I wrote to Newair and asked and they said "Yes, there's a 120 v plug!" They didn't answer the part about amperage and tripping the breaker.

My garage outlets are 3-prong, the breakers are labeled 120/240v, 20 amp. Should I be concerned?

I'm not married to that heater, BTW. If someone has a better suggestion, please share. I'm not interested in hard-wiring something because the garage is still un-finished. I just want it warm(er) when working out there and not burn the place down.