Gee, I'm going to run home right now and replace all of my 40 watt incandescent bulbs with these wonderful LED bulbs. And the best part of it is this will cost me nothing, since my home does not have any 40 watt bulbs. They are too dim and inefficient to be worth using. 40 watt bulbs provide less than 75% lumens-per-watt of light and over 1/3 more heat-per-watt when compared to a 100 watt. The lumens-per-watt relationship for tungsten filament incandescent bulbs is not linear, it is logarhithmic based on this table:
http://en.wikipedia.org/wiki/Incandescent_light_bulbComparison of efficacy by power
(120 Volt lamps)
Power Output Efficacy
(W) (lm) (lm/W)
5 25 5
15 110 7.3
25 200 8.0
35 350 10.0
40 500 12.5
50 700 14.0
55 800 14.5
60 850 14.2
65 1,000 15.4
70 1,100 15.7
75 1,200 16.0
90 1,450 16.1
95 1,600 16.8
100 1,700 17.0
135 2,350 17.4
150 2,850 19.0
200 3,900 19.5
300 6,200 20.7
My semi/enclosed fixtures are limited to 60 watts by the manufacturer due to heat/fire hazard issues. Other lamps have 100 or 150 watt bulbs. Most of the 60 watts have been replaced with CFLs.
I'm still waiting for affordable 2000 and 3000 lumen CFLs to replace the others. Part of the problem with CFL and LED replacement bulbs is they appear to be only affordable to manufacturer in the low-light-output bulbs and these are not good replacement candidates for lights and lamps that are designed for single medium to high output bulbs, say 100-200 watts.
Many single bulb floor and table lanps are not practical to convert to multi-bulb arrays to get the needed lumens with low lumen bulbs. Many of these lamps are also designed for an omni-directional bulb to provide a balance of direct-down light along with diffused light through the shade and reflected light bounced off of the ceiling. LED lights are very directional, behaving like reflector incandescent bulbs, and are mostly suitable for aimable light installations using multiple bulbs/lamps to replace a single omni-directional bulb.
Given the higher unit costs with lower lumen outputs and limited ability to replace the mature-design of incandescent bulbs, LEDs and CFLs still have a ways to go to replace them wholesale, especially if they require replacing the existing fixture or lamp for no other reason than to compensate for the limitations of the current crop of alternatives. This doesn't sound very efficient to me...
