Dear Reader:
One of the most important indicators of an LED lighting fixture’s energy efficiency is its Power Factor rating. While the meaning of this metric eludes some Facilities Managers, it’s really very simple as to what it means, and how it’s calculated.
Power factor is the measure of how much electricity is actually being converted to work – the creation of electric light. Looked at conversely, the electricity that is not being converted to lumen output, or footcandles down on the task area, is wasted consumption. For those particular electrons, you’re paying for kWh that is buying you nothing, so this portion of the electricity consumption is just flying out the door.
Every electrical device, machine, etc. loses some of its useful input energy to waste … the question is always, then, ‘how much’. As power factor metric is typically expressed in terms of a percentage, a good power factor rating for an LED lighting fixture would be in the neighborhood of 90%, which is to say that the fixture loses no more than 10% of it’s input energy, converting what remains to light.
More technically, power factor is the ratio of useful power in kilowatts, or kW, divided by what we’re charged for in kVA (kilovolt-amps). So it tells us how much useful power we’re getting for the power we consume.
There are at least two additional negative impacts to low power factor, beyond the obvious inefficient energy usage. Heat damage to insulation and other circuit components can become a real problem. And conductor and equipment may need to be sized upward as well, to ensure that enough useful energy gets to the unit, for it to do its work.
There is a wonderful YouTube video available that explains this in very simple terms, and you can find it here: Power Factor Explained. It’s produced by a gentleman by the name of Paul Evans, who founded his website known as TheEngineeringMindset.com in 2015, with the mission to help students, engineers and like-minded people learn technical engineering topics through short, simplified tutorials. A narrative on Paul and what he’s attempting to accomplish is here: About The Engineering Mindset.
We are an industrial lighting contractor, and not an engineering firm. As such, we’ve found that Paul’s ability to break topics down into useful, understandable bites on a whole host of topics has been invaluable.
The prudent Facilities Manager, intent on continuously learning his/her craft, might take a look.
