When dealing with these, as previously stated, better to go big with adjustable settings. They are not terribly good heaters compared to fueled units, but probably a ton safer.
I used to use similar units to keep my boats engine bay warm up North, but at home, I preferred the kerosene units I inherited from my grandparents.
Down here, I once used electric bar type space heaters in my old apartment back during the freak cold snap of 2009 (electricity included, not my problem lol), but they sounded like science fiction mind control weapons and scared me half to death. But man were they effective!
I slept warm, but moved everything around to create a 10 foot DMZ around it in the middle of my tile floor, and kept two fire extinguishers handy.