My favorite outdoor hydroponic system is the Ebb&Grow system made by C.A.P.P., because I feel it is able to handle the rigors of the outdoors while allowing you to grow an insane amount of veggies in a small area. It's about $400, but it's been the best investment i've ever made. The system comes with a 50 gallon reservoir to hold the nutrient solution, and 12 buckets to hold your plants. The beauty of the system is it's scaleability, I could easily run 24 plants or even more off of a this system by just attaching more buckets to the main controller bucket. Right now though, my backyard can only handle 12.
I did this grow last year as one of my first major hydroponic grows and I was BLOWN AWAY at how much food was produced in this tiny area in my little suburban backyard. I mean I was literally giving away bag-fulls of tomatoes to my co-workers and even donating huge amounts to the local food bank, and that's after my family of 4 ate as many as we could. And that was just the tomatoes.
The system is really simple and doesn't require much energy at all. It runs on a timer, and basically all it does it flood the buckets for about 15 minutes every hour and then drains the water back out. When the timer kicks in, a small pump takes nutrient solution from the rez and pumps it into a controller bucket which is the same height as the 12 buckets attached to it which hold the plants. Gravity then fill up each bucket until it is level with the water level in the controller bucket. The whole thing is run by 2 float switches in the controller bucket that let it know how much water it needs in order to fill up all of the buckets via gravity. Once the cycle is complete and it's time to pump it back out, water is extracted from the controller bucket and once again gravity does most of the work in emptying out your plant buckets. Plus, with a 55 gallon rez, the water stays extremely stable and is easier to cool as it just is such a large volume of water. I could go 2-3 weeks without checking pH easily.
This grow includes:
Anyways, here's a little gallery of the system along with a little PVC housing I made so I could shield it when the rain came in too hard, all pics are in chronological order. Enjoy!