I hope this topic hasn't been covered before. I searched and was unable to find an answer to my problem. I am contemplating a grow tent that is 4' X 4' x 7'. I only want to grow one plant at a time, because I don't smoke much, have NO intention of selling anything, and don't want to build up a massive stash. \nMy question is thus: what size light should I get? I was gifted a 400 watt HPS/MH switchable ballast, but the last time I plugged it in it sparked, started buzzing loudly, and shocked me pretty bad when I touched the case of the ballast. This is when it is in the OFF position (as opposed to the MH or HPS position). It also has trouble starting the HPS bulb (sometimes it will start, sometimes not). So I don't think it's safe. \nSo I have to buy a light, I'm trying to decide whether I would benefit from buying something larger than a 400 watt, considering I will only have one plant at any given time. I've read a lot about lighting, and the consensus seems to be that a 600 watt is perfect for a 4' x 4' room, but everyone talks about how many plants you can cover with that wattage and area. I have no desire to achieve a maximum yield for my space. I simply want to achieve a maximum yield from one plant at a time, while wasting as little electricity as possible. \nWhat I've been looking at thus far is a dimmable ballast (either 1000 watt or 600 watt), or a regular 600 watt, or possibly the new 860 watt Philips ceramic metal halide. Or if it would work, even the 330 watt ceramic. I've read good things about the ceramics, but I don't know enough about lighting to make a decision. Thanks to everyone for any assistance possible! \nTLDR: What wattage and type of light should I buy to maximize yield from ONE plant (and only one plant at a time) in a 4' x 4' x 7' tent while minimizing electrical costs. Thanks!