# Any reason to acquire more watts than really needed?

Basic question (again):

I have a LED-strip that requires 5V, and each LED (150 in total) requires about 60 milliamps. Calculating everything, I need 3 of these LED-strips (450 LED in total). This in turn tells me that they require 27 000 milliamps (27 amps), which is about 135W. Which means I need an external power supply to power them. I think about buying a 5V 40A (200 W), which should be sufficient(?).

But, is there any reason that I should not buy anything with more watts (250 or 300)?

Thanks for any help!

• i would actually rather have 3 different 10A (or 12A for margin) supplies, so that my cables weren't heavy and/or a burn risk. Aug 12 '19 at 19:35

Are you sure every led is 60 mA? Or you mean maybe each Red, green and blue led inside each led (3 x 20 mA).

Why would you need more? If you mean to control it with an Arduino Uno, that MCU (including the LEDs etc) is high likely more than a few hundred mA. So the only reason why you need more, is if you want to control later more LED strips, or any motor or other power hungry external devices.

• Thanks for your reply! Yeah, I meant 20 mA each red, green and blue. Based on what you write it seems fine to go with 200W, so I will try that. Thanks again for making things clear! :)
– Araw
Aug 12 '19 at 19:39