Cost of running T5 set ups?

[naoki]

I'm particular interested in LED since it does not generate heat and takes little power to run.

The heat part is generally true, but the second part is only partially true; not all LEDs are as efficient as T5 (or even with T5HO). Depending on design, there are huge variation in efficiency. Generally, older and/or cheaper means less efficient than T5.

Anyways, for those who mentioned that LED with "white light", can you please mention the product name so I can look up?
I thought only those creepy blue and red LED were suitable for growing orchids?

This appear to have a good efficacy (around 133lm/W) among easily available options:
http://www.homedepot.com/p/Philips-...-4000K-Linear-LED-Light-Bulb-453852/205807273
As I mentioned in my post, I'm not so fond of the idea of direct-fit T8 LED, but it is slightly easier.

The following company is known to make products which were tested to have high efficiency:
http://www.bmlhorticulture.com/full-spectrum-grow-lights/
They do make white LED series.

If you can do DIY (needed skill: drill holes + tap aluminum and strip wires, no soldering required), I recommend Bridgelux Vero 29 or 18 (or Cree CXB3070, but more expensive) for ease of assembly, high efficiency, and inexpensiveness.

Also, regarding K, I was told that it has to be 5000K or above to successfully grow orchids.

Some people prefers bluer light, but I don't know where this is coming from. 6500K is frequently marketed as "daylight", and people are confused that "daylight" spectrum must be better for plants. From my PPFD measurement of many light, I would say 3000-4000K LED is pretty good. Also human eyes see the light differently from plants, and higher K light appears to be brighter to our eyes.

Last, the distance between the light bulbs (say, LED and T5, but I guess the number of the bulbs of course matter a lot) and the plants.
I don't want them to be too short for the flower spikes development.
How do you deal with that?

As you mentioned, the distance depends on the amount of total light. This could be influenced by the output as well as the beam angles. For example, Spot-light (instead of flood-light) type PAR 38 has narrower beam angle, so you can place it further. Here is an example:
http://creebulb.com/products/reflector/90-watt-replacement-bright-white-par38-spot-led-bulb
It's from a great LED company, but it is only 83lm/W, though (most of white PAR38 and A-type bulbs seem to have fairly low efficacy).

When I was growing Paphs under T8, the plants were 6" or so from the bulbs. When they spiked, I put them around the edge (the inflorescent grows beyond the fixture). So there was not problem. Watering was a bit tedious, though.

 

[papheteer]

I've had my t5's for 3 years and I've only replaced one. Output hasn't changed much.