I have not heard of one but you could contact Onset Technologies which create data loggers of all sorts. They may be able to supply you a light sensor that could be paired with a mechanism to turn off the lights when enough natural light was present. I share your concern about energy waste. What is your goal? Do you someday want to build a commercial operation or are you looking for a hobby structure? We are in the process of building an energy efficient greenhouse and we considered artificial light to supplement the natural light but in the end did not really pursue it. We do have LED lights but just in normal fixtures and using typical warm white light. We were not interested in the blue and red LED lights because when we artificially light our greenhouse, it will mostly be for spending time in it. However, that might make sense for your application. No matter what artificial light you use, nothing comes close to the intensity of the sun. If you can use natural light for most -if not all- of your needs, you will be in good shape. For our GH, we are using windows strategically to get the most light and heat by putting them on the south side and a few on the east but none on the north. Everywhere else is R29 insulation which keeps things at a steady temperature. Another thought, Logee's Greenhouse is an hour away from me in Connecticut and they sell tropical plants and trees. They use NO supplemental light and they are a commercial grower that sends their plants all over the country (Martha Stewart is a big fan). Their visiting hours are restricted in the winter because there is not enough light after 4pm for people to look around so they actually reduce hours when most stores are extending them for the holiday shopping season. They have a lemon tree that is over a century old that is producing HUGE fruit and many other fruiting trees that are pretty productive. Maybe you don't need supplemental light at all.

I believe redshirtcat grows under lights in winter, I think he uses HPS but im not sure. I do know that there are different benefits of using both HPS and metal halide. I use daylight fluorescent for seedlings in winter and they do just fine. hang tight smart guys will chime in. Mike

First, callas (Zantedeschia species) are not really lilies (true lilies = Lilium species) but arums, so you may get a better response posting in the Aroid forum. Second, I've never heard of anyone attempting to grow them hydroponically but theoretically I guess it could be done. The attached link has some info on growing them under lights (greenhouse conditions) but may be more appropraiet to potted plants. Here is a link that might be useful: callas under lights

Ross, I like out-of-the-box set-ups. My 400-watt HPS had everything I needed, I just needed to attach a few screws. But just to throw a monkey wrench into your plans, have you thought about LED lights? They are mo-re expensive to buy, but they have lots of benefits, especially if you count bulb replacement, the cost of electricity and AC costs in summer. There are even some models that allow you to control the amount of Red and Blue light, depending on the growing stage. I just bought a 125 watt panel (list price, $209) that covers the same area as a 400 watt HPS from this store but I don't think they sell the adjustable ones. But from another site it tells you how many panels you need. For your plants, it looks like 2-4 panels since you need medium to high mols/day. The cost of the fixtures may end up being the same but you would be looking at using 250-500 watts per hour instead of 1200-1800. Of cou-rse, you can always buy one HPS/MH lamp and a LED panel and see which works the best! Mike Forum owners: will you PLEASE quit adding links to my messages.