Quote Originally Posted by outerspace
Theres just one point I dont think anyone has touched on here yet, is the efficiency of LEDs. They can be around 10-20% efficient, meaning 80-90% of the power you put in is turned into heat, and this is not much better than HPS. More power is wasted into heat as you convert AC to DC, and then even more when you regulate your DC to 20mA.
He's right. LEDs are way more efficient than incandescent bulbs, but they're not 100% efficient. Here's the chart:

Luminous efficacy - Wikipedia, the free encyclopedia

An HPS bulb has a luminous efficiency of 22%, while white LEDs have efficiencies from 3.8% to 10.2%, with only prototypes reaching up to 22%.
So, by using LED bulbs for growing, you are spending more money per bulb, and you are going to be spending more money on your electricity bill.

Sounds pretty stupid to me.