LED Bulbs - Which Measure is the Best Indicator Of Efficiency
Watts per lumen is the way I evaluate With more lumens per watt  is the best way because you have to look into the numbers to figure out how it was calculated for savings based numbers. I have seen 2 LED lamps with the same voltage &amp; lumens show quite different saving numbers. The last thing to think about is the color frequency. For my home and plant I go for higher numbers for 2 reasons, 5k+ helps to reduce SAD and looks more like daylight. Down around 3k looks yellow/ orange and althow some lamps may score higher energy savings at a lower # this is based on incandescent lamps that match this color.  the "warmer 6k lamp" used less power and to the human eye looks brighter the older technology led were advertised as more cost savings based on lower initial cost (due to older technology). Added per request; I live in Oregon where SAD is a problem because of cloudy sky's a broad spectrum higher color frequency light ( in the blue spectrum) helps reduce the affects when I worked at HP the plant was relamped with 6k lamps to combat this issue. Some rooms use only yellow light to prevent the photo masks from being exposed a test was done in 1 area where the operators that worked in the photo area spent at least 15 minutes with direct exposure to 6k &amp; 6.5k at higher than normal light levels and the "sick time" for the area dropped after that they did the plant relamp and 3-4 years later the average "sick time" across the entire site was reduced by 3% according to the site health nurse.