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I recently bought this: http://smile.amazon.com/gp/product/B00II1MN5I and am planning on using it for under cabinet lighting in the kitchen.

Power adapter:
Model: TNS-1220
Input: 100-240V AC, 50/60Hz
Output: 12V DC, 2000mA

I want to keep it plugged in all the time and control it via some sort of switch/button to turn off/on. If the power adapter is always plugged in, would it consume electricity (it has an LED that lights up when plugged in). If so, would it be negligible?

Basically I want to know if I should:

[outlet] -> [power adapter] -> [control switch] -> [LEDs]

or

[outlet] -> [control switch] -> [power adapter] -> [LEDs]
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  • \$\begingroup\$ I'd go with a standard light switch under the cabinet and switch the supply to the power adapter for the totally off solution. \$\endgroup\$ – Spoon Aug 25 '14 at 22:04
  • \$\begingroup\$ At 24W you could leave it on 24x7 \$\endgroup\$ – user51925 Aug 25 '14 at 22:31
  • \$\begingroup\$ Citation on 1W @venny \$\endgroup\$ – Passerby Aug 25 '14 at 22:45
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Power draw from a plugged in power adaptor that is not in use, is measurable, but negligible in the long run. A 2 Amp switching supply like that will cost you maybe a buck or two a year, if left unused but plugged in 24/7. Negligible is subjective.

But the supply for that led strip, is just a power supply. It has no off mode, no flashing, nothing fancy. So unless you disconnect the strip, the supply will be powering the strip. Unless you disconnect the supply.

So you need to switch the outlet.

A simple method is a dollar store switched outlet adaptor.

enter image description here

Or a power strip.

enter image description here

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A 24W Energy Star compliant external power supply (AC-DC) should not draw more than 300mW when the output is not loaded. http://www.energystar.gov/ia/partners/prod_development/revisions/downloads/eps_spec_v2.pdf

However, there is no indication that the AC adapter sold with that LED strip is Energy Star compliant or even UL/CSA approved, so there are no particular guarantees as to efficiency or safety (electrical or fire safety). Caveat emptor.

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