Aug 25, 2013
May, 2013 observations here don't include yet-to-be offered Sylvania 70732, 900 Lumens, too bright for sight comparison. I don't really accept that the Cree 60W LED bulb has brightness 2.4. The 4" Glimpse, dimmed to B2.4, ...
The "Making Money" post is informative of payback math. I am confident no more-useful or more-accurate study in this, exists. Please try, use and comment upon the math. The nugget of the process is that if a 100 watt incandescent bulb gives the needed illumination, how much can you save if the same level of illumination is achieved by better means.
At December, 2013, add to the payback math, bringing in the package claim, and more from the Sylvania product web page:
The package claim is savings of $238 electricity over 35,000 hours. It is the $239 number in the table above, against operating a halogen 75 watt PAR38 flood light. This halogen light is concentrated in probably a 40° beam angle, vs. 120° beam angle with a directional plate fully revealed. I have never owned a 75 watt halogen like this, but have collected many halogen 50 watt PAR 30 during LED retrofits. Consider this photo comparison, illumination from my test stand:
The Sylvania table claim of 1060 lumens for a now-obsolete 75 watt halogen flood would correspond to B9.4. I think it will at best match a B8 LED disk. I despair of comparing my math with that of Sylvania, for this obsolete halogen light.
Look only at the Sylvania table for the comparison with a 100 watt incandescent. The Sylvania table shows $335 electricity savings over 35,000 hours. My electricity savings number is $385 - 25 = $360, $25 higher. The higher number is with matched illumination, by 50% dimming of the LED. It is proper to add also the difference in cost of replacing burned-out lights, $55 - 19 = $36. If by dimming the Sylvania 70732, I maintain the illumination of a 100 watt incandescent, I will save a total of $396 over 35,000 hours, not just $335. Know too, that securely-wired LEDs like this will shine on in full brightness for more than 100,000 hours; savings continue.