I bought 2 high intensity 125W spiral CFL, 5500K daylight bulbs from ADORAMA, NYC. The bulbs are standard base, and will screw into any ordinary standard lamp sockets. The bulbs are about 8" -10" OAL and I hang them down, vertically, so they run the parallel to the length of my plant stems and wash the whole length of my plants with light. Why? My caudex plants lose all their top leaves, so why waste all the bulb's highest intensity light at the top of the leafless plants? Caudex plants have photosynthetic stems, branches, and caudex. These greenish parts of these plants substitute for the leaves, and will continue to make food while plants are quiescent/dormant. So I keep these parts in the intense light. I think I read that 125 W CFL are roughly the equivalent of 600W incandescent bulbs.
The bulbs cost me about $13.00 each. Not exactly the ideal 6500K color temp....but these bulbs are better than nothing and they require no special sockets, timers, reflectors, cooling fans, etc. Plug them into an ordinally socket and your plants have light. I stick my plants on top of a waterproof baking pan, hang the lights between the plants (vertically), and the plants seem happy. Two bulbs put out a lot of light! I rotate the plants so that each gets to spend some time growing next to the maximum light output.
This is the set up I use to get my plants thru the long dark winter months. BTW, I only have about 5-6 plants to light. It's cheap, and it helps prevent my costly fat-plants from failing.
Hope this helps.
