Like said, as far as power consumption goes, LEDs use much less than a T5 or CFL. Giving off very little heat is nice also, for those setups prone to that issue. I know my CFL and T5HO equipped tanks warm up quite a bit due to the lighting.
Problem is, to get an LED fixture for a tall 29g that's going to support plants is going to be expensive and still have to pull 30-40 or more watts anyway, so your savings may only be with the lower heat output.
IMO, it's a matter of waiting it out a bit longer. Look how inexpensively you can get a T5HO fixture for now. Won't be long store-bought LED plant-ready strip lights will be the norm and be inexpensive too.