as long as you calibrate it...I can't sit here and tell you how accurate it is because I don't have anything to compare it 2...I would have to have the $500.00 deal to to compare and in that case I wouldn't need it then...I mean if you can afford the apogee sensor I would get that...I could afford to buy it I just refuse to...I had problems before I had anything and not so much now so it's up to you in what direction you go...Wish ya all the luck in the world...was just trying to keep you from making my mistake...the bright white are not like the old led's...you can slam a plant with way too much light...