LED power supply by Evivak. The appropriate power supply for an LED strip is calculated by multiplying its consumption in Watt per meter with its length. However, it is recommended to purchase a power supply that supports an additional 20% of the required energy in order not to work at its limits. In this case, the power supply of the product is 20 Watt, which means it has the ability to power, for example, a 5-meter LED strip with power consumption of 3.2 Watt per meter.