Hardly accurate at all. They are spec'd at 2ºC up or down (that is just under 4ºF) so if it reads 90º it could be anywhere between 94º and 86º add the hysteresis or 'swing' is 3º low I thought it was 2º over the previous poster stated 3 either way added to the error rate it is a huge range (worst case 7º under and 6 or 7º over).

To my mind it is unacceptable in some circumstances. The most specfic is when used with a UTH that is taped or fixed to a tub. The swing and error can make a for a very large temp spike. Heavy things like takes (glass is slow to change) it isn't so bad just not to be trusted accuracy wise. It is sort of ok in a rack although I would not trust it safety wise either it seems silly to entrust multiple animals to a thermostat designed to heat dirt for seedlings.