These "things" have been hawked around on the internet & video shopping channels for years - often with many "very negative" comments, and frankly they look pretty damned dangerous to me - 500W claimed dissipation in a box about twice the size of a wall wart USB charger (the latter are generally rated 5V 2.1A max output = 10.5W)!
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Anyway, how the hell you would expect 500W (if it is really even that!) to heat a room that is probably below local ambient to start with is beyond me as you'd need at least 3000W, and preferably a lot more, to result in ANY significant rise in that temperature!