This new note is Issue 17 in our ongoing series and is titled "Lux & Lumens: Light Measurement Metrics". Many here are already familiar with our Standard Specification Sheets (SSS) listing lumen outputs and other lighting service metrics. These Specifications are more appropriate for a technical audience, whereas this new Note looks forward to consumer appropriate labeling and the challenges associated with conveying technical performance to the average customer.
Lighting metrics are not widely understood. Lumens (or total luminous flux) is a measure of light coming from a source, whereas Lux (illuminance) is a measure of the light incident ON a surface. Our technical Note discusses the differences between these metrics and makes a case for lumens as a standard, consumer-facing, reporting metric. Lumen values are widely given for LED lighting products, this is consistent with the larger lighting community and is really the only way to report the lighting performance of a lighting product with a single number.
Unfortunately many consumers will not be familiar (much or at all) with lumens. Other programs have dealt with this by pushing an education agenda - the Lighting Facts label started by the US Dept of Energy is an example where they standardized the label and are counting on stakeholders to educate their customers. One of the first things I do when introducing lumens is to give an equivalency to a 60 watt incandescent bulb - this is somewhere in the neighborhood of 900 lumens and many grid-connected consumers have a rough idea of what this means. We've discussed a similar approach in our program, but a 60 watt bulb is probably not the right comparison (its quite imperfect anyway). Could another equivalency work? It probably would be a candle or a lantern, but as far as we can tell these vary widely and may not add value (and could potentially add confusion and would thus be counterproductive).
This new Note is in many ways a start for this conversation, one we hope to engage the larger stakeholder community in as we consider options for encouraging consumer reporting that adds value to the market.