turn the light on and leave it on for about an hour, go back to it, and put your hand near it, feel the heat, if it's really hot and you're not even touching it, then it's useless

i would just try to grow some other types of plants under it, maybe a tomato and just some flowers, let them sit under the light for a while just to see how they do...you'll see within the first week prolly if they're taking to it well
jadeius Reviewed by jadeius on . are they worth being free?? because a few events over the past few weeks I ended up with some lights and balast from a friend who use to grow. I've bought a hps and a mh 400w and have been trying to find a new cheap way to keep some mothers and some veg plants going when they are both filled and need more room. Anyways I got the free stuff and have no info about them, they are mercury vapor lights, one 175 and one 100w lights. Has anyone used them to grow and are they going to be worth even trying to put up?? I mean Rating: 5