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Question is about those LED drivers that convert 120V (or whatever your house voltage is wherever you are) AC to 12V DC for driving LED light strips and the like.

Do they draw power when plugged in, but not loaded, i.e. the lights are turned off (switch on DC side)? If so, do they draw full power (e.g. 100W), or some kind of standby level of power?

TIA.

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  • meanwell claims 1/2 watt no-load consumption for their 12v drivers.
    – dandavis
    Apr 3, 2021 at 20:13

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12V constant-current power supplies have a small "standby" power usage of a watt or three depending on quality, when all the DC loads are switched off. You can measure this by plugging it into a Kill-a-Watt. Other than that, they draw whatever power is used on the DC side, plus a few percent for conversion losses.

12V LED strips typically use a constant-voltage power supply, which is simply called a power supply. They are often marketed as "drivers" because it sounds cooler, but that's wrong. Any 12V power supply will work for LED strips.

(a real driver is a constant-current source and must be custom-matched to a very particular array of raw LEDs. LED strips don't work that way).

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  • not "any" 12v power supply will work for a full 5m of modern strip lights; they need 2.5+ amps, and most 12v wall warts only spit out 1-2 amps. Also, some common older ones (eg RadioShack beige ones sold as universal replacements) are just rectified and lightly smoothed but not regulated, so the odds they will output 12.0v on any given strip is low.
    – dandavis
    Apr 3, 2021 at 20:20
  • @dandavis Sure, but that's basic stuff that's prerequisite to doing any sort of work like this. Answers don't need to cover all bases, they'd turn into disclaimers if they tried.
    – Harper - Reinstate Monica
    Apr 3, 2021 at 21:43
  • @dandavis We're talking a 150W power supply here for 28' worth of light strip, so...
    – Huesmann
    Apr 4, 2021 at 21:46

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