Choosing an LED Power Supply

Determining what power supply is needed for your low-voltage LED project

LEDs are generally operated at 12V or 24V and require DC (Direct Current) Voltage. Outlets offer AC (Alternating Current) at High Voltage (generally 110VAC in the United States.)

Therefore, LEDs need a power supply to offer the required DC low voltage current.

Power(Watts)= Amps x Voltage


LED power supplies are most commonly available in 12V or 24V. It is important to select the voltage that matches with the LEDs that you plan to power.


Consider the total wattage of the LEDs that you plan to run. Example: If you want to buy a roll of LED Flex ribbon and the entire 5 meter roll is rated at 21 Watts with a total of 300 LEDS, this means that each LED is .070 Watts.

If you plan to cut off and use 150 LEDs, that would equal 10.5 Watts.  You will want to select a power supply that provides 20% above and beyond the needed wattage. In this example, 10/5 Watts x 1/2 = 12.6 Watts.  A power supply with 15 Watts or 20 Watts would do fine in this example.



Not all power supplies are intended for outdoor use. If you are unsure if the power supply is water resistant, please check the specifications to look for an IP Rating.

IP “Ingress Protection” will indicate how much water protection is provided in the power supply or LED lighting design. Generally, IP67 and above is good for outdoor use (suitable for wet areas, but not for submerged).



Many lengthy pieces on the web offer in-depth details on this issue but we will provide a bare bones explanation here.  The short answer is that you can use either “Class II” or “Class 2” depending on your needs.

  • Class 2 relates to the maximum power that the power supply can deliver (example: 100 Watts).
  • Class II involves safety and insulation to protect the user from shock.

Note: Class II power supplies have a two-prong wall plug and Class 1 Supplies have a three-prong wall plug.



Most D.I.Y. LED projects involve LED bars or LED Flex ribbons that have onboard resistors or internal drivers that are in place to limit the current. As the current limiting is already onboard, Constant Voltage drivers are more commonly used.

Constant Current drivers are used for LED applications in which the LEDs do not already have current control built in. The constant current driver delivers a precise current regardless of fluctuations in the supply voltage.

Constant Voltage drivers have a pre-determined voltage and variable current.


Selecting a UL recognized power supply is always recommended.


Take a look at JKL’s ZPS-2435 – a 24V 35 Watt Power Supply (Ref. LPV-35-24)

ZPS 2435 JKL Power Supply (Ref. LPV-35-24)

The unit offers 35 Watts of power and would be suitable to power LEDs up to 28 Watts.

Take a look at some of the specifications in the ZPS-2435 power supply tech sheet:


  • Green Arrow: Indicates this is a “constant voltage” power supply
  • Pink Arrow: IP67 Water Protection Level (suitable for most outdoor applications)
  • Blue Arrow: UL listed, Class 2 power unit
  • Red Box: Basic details including voltage, wattage and current (Amps).



Contact JKL with questions about selecting power supplies for your LED projects.





Listed in Do It Yourself Projects, Tips & Tools