1 Helpful?

Phantom load on Occupancy Sensor?

I recently learned (to my delight) that Lutron now sells occupancy sensors that also work with CFL's and/or LED's (Lutron Maestro - http://www.lutron.com/TechnicalDocumentLibrary/3671632a_Maestro_Occ_Sens...).

I would like to use occupancy sensors in our deep energy retrofit (http://delafleur.com/blog/) - but now have the nagging suspicion that in order to operate (constantly monitor environment), they have to draw a phantom load. Question:

- Does anyone know if they do draw a phantom load?
- If they do, does anyone have a sense about the load size?

Asked by Marcus de la fleur
Posted Dec 18, 2012 12:52 AM ET


7 Answers

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Check out this Quick Start Guide from Watt Stopper on a similar product:

It's an occupancy sensor that draws 8 mA
8 mA = 0.008 amp = 1 watt
This device uses 24 watt hours per day, or 8,760 watt hours per year = 8.76 kWh per year
That's about $1 worth of electricity per occupancy sensor per year.
Another way to look at it: 24 watt hours per day is equivalent to turning on a 12-watt CFL bulb for two hours a day, every day, all year long.

Answered by Martin Holladay
Posted Dec 18, 2012 5:29 AM ET
Edited Dec 18, 2012 9:02 AM ET.


Thank you Martin! The info you sent me got me hooked even more. I went back through the Lutron specs to see if the the current consumption is listed - but it wasn't. I called Lutron tech support. They said that they don't have that info. He indicated that the current draw may be 0.5 mA - but that is pure hear-say right now. I think I try to find someone with a mA meter and measure it myself. That way I should have piece of mind...

Answered by Marcus de la fleur
Posted Dec 23, 2012 11:54 AM ET



I just measured a few of these sensors and was rather disappointed in the amount of parasitic power consumption there is when in the off state. A vacancy sensor should not need any power when the switch is off.

Here are the results of what I found so far:
Make Model P/N Poff (w)
Lutron Maestro MA600G 5.1w
Leviton IPP15-1L 5.2w
Legrand Wattstopper RS-150BA 0.9w

Lutron Maestro MW-600 w/ MR companion dimmer 3.8w

I made the same analysis as Martin and I find it infuriating that a switch in the off position uses so much power. For the 5watt Lutron and Leviton products it is like leaving a 60w bulb on for 2 hours a day! An EV could drive about 150 miles on a year's wasted power from one switch. In a conscientious house hold they don't make sense. Sadly, I have teenagers so it might make sense.

The Lutron MA600G also leaks almost all of it's current through the lamp! This is an incandescent dimmer/sensor so the lamp doesn't glow. It could be that the newer CFL compatible ones will work better, since they can't drain through the lamp. When I screwed in a CFL the MA600G flickered the bulb and could not be shut off! I will test the CFL compatible ones and report back.

All of the above switches have glowing LEDs when off. I also find that irritating. Since these are programmable switches they should have the option of being DARK.


Answered by Chris Arai
Posted Feb 12, 2013 2:53 AM ET


Almost ANY electronic device will use energy even in the "off" position. Meter your computer or TV and you will see the same. As for leaking current across the lamp, that is how some are designed. In order to operate they must have a current flow. As most switch locations did not have a neutral available due to the common practice of taking a "switch loop" of only the hot conductor down through the box the only way to have that current flow is either passing some current through the fixture (as you noticed) or to utilize the GROUND conductor for the return path (something that UL allowed and which the NEC therefore could not forbid). All new construction operating under the 2011 NEC should have a neutral run into the switch box regardless if it is to be utilized at that time unless the system in in conduit where one could be added if needed later.(NEC 404.2 C). I would try to find a commercial occupancy sensor that requires a neutral connection to prevent those issues.

Answered by Nathan Spriegel
Posted Feb 12, 2013 4:13 PM ET


It is a shame so much power gets used. For most appliances they are providing some "function" in the off state, usually only to respond to the remote or provide a timer function. I contacted Wattstopper and they point out the function they provide is the locator lamp. I would appreciate if they would make this feature optional. A manual on vacancy sensor in theory does not need to provide any functions.

My entertainment center uses 25w when "off". Infuriating. I need to find a smart power strip. Any suggestions?

Answered by Chris Arai
Posted Feb 14, 2013 11:36 AM ET


Q. "Any suggestions?"

A. I use a dumb switch. Just disconnect the power when you aren't being entertained by your entertainment center.

Answered by Martin Holladay
Posted Feb 14, 2013 11:49 AM ET


We used what we call a "kill switch". It won't kill you when you use it, but kills the power to the outlets in a room. Would require some re-wiring... For more details read: http://delafleur.com/blog/?p=3400
For an image go to: http://delafleur.com/blog/?p=3740

Answered by Marcus de la fleur
Posted Feb 14, 2013 11:32 PM ET

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