Comment Not 200 lm/W (Score 1) 421
I looked at the data sheet of the Cree XLamp MK-R and even though they state "Delivering up to 200 Lumens per Watt" in the header, looking closer the best I found was nominal 147.25 lm/W and top luminance bin = 157.51 lm/W (which I wonder if I can order and at what price?).
Forward voltage is 11.7V at 700mA = 8.19W
The highest lumen output I found was 1206lm at 5700K and 6500K at a CRI of 65, which makes an efficiency of:
1206lm / 8.19W = 147.25 lm/W
If you can live with such a low CRI and cold white then that isn't bad, but not even the best.
I have seen 150 lm/W from other manufacturers at 5000K and CRI 70, which is a more natural white and slightly better CRI and perhaps even with a better R9 (Red), but the Cree data sheet doesn't state the individual values of R1 to R14, it is difficult at this point to compare.
What is however very good of this Cree LED is the thermal resistance at 1.7 C/W. Together with the max. junction temp at 150C it provides a component that is very well suited for high power and high luminance lamps.
An interesting development, but not the 200 lm/W I was hoping to see.