Tim Wescott wrote:

Anyone used 'em?

I've got a high-bay shop with about a dozen 8' florescent fixtures, only
a few of which work. I'm thinking of replacing them one-by-one with
these things, whenever the planets align and I'm extra flush with cash:

http://www.homedepot.com/p/Lithonia-...-LED-High-Bay-
Light-IBH-11L-MV/203812710
WHOA, those are expensive! I have retrofitted 2 2-lamp fluorescent
fixtures in our kitchen, and am pretty happy with them. They've been
running for over 6 months, now. The kitchen lights get a LOT of
use in our house, so those are the ones I've done first.

I have used a string of 20 Cree XPEBWT-01-0000-00CC2 LEDs to
replace two 48" fluorescent tubes. These things are $1.75
each, total $35. I buy them from Digi-Key. For a power supply,
I use a Thomas Research Products LED25W-72-C0350, also from
Digi-Key, part # 1121-1052, about $27. So, total cost is about $62. The
output is supposed to be about 4580 lumens. I used a photometer, and
it SEEMS to be actually brighter than the two 48" fluorescent
tubes, but the light is a bit more concentrated in a single
line, so both my eyes and the photometer could be fooled. Anyway,
it appears to be quite good at illuminating the kitchen. You DO
need a diffuser over the LEDs, they are seriously blindingly bright!

I measured the power draw of the ANCIENT ballast, it was 101 W.
The LED system with the mentioned power supply was 21 W. This
was measured with an actual power meter.

These LEDs are rated at 101 Lm/W, which is quite good. Any higher
efficiency and the cost goes WAY up. The power supply is supposed
to be 86% efficient, I think.

The LEDs are surface mount, so I got some strips of 2" wide PC board
material, and cut narrow slits in the copper at 2" intervals. I soldered
the LEDs across the slits. The copper material acts as a heat sink to
keep the LEDs cool. Then, I suspended the PC board strip in the middle
of the fixture with some loops of insulated wire.

I will probably so more fixtures as I get time.

Jon