Can I use Watt to determine the power of a flashlight
Watt is a unit for power consumption
The short answer is no, Watt shows how much energy the product consumes, not how much light output (lumens) it provides. That is why you should not look for the amount of watt consumed, when buying any kind of light. It will only tell you how quickly it will drain the battery, and not how much light it produces.
It is also worth to know that 1Watt halogen and 1 Watt LED do not produce the same amount of light. The LED Chip is more efficient and will convert much more energy to light than the halogen bulb.
It is important to keep in mind that the more power consumed the more heat is produced, and heat will always result in a loss of energy. That is why all of our flashlights and headlamps are equipped with a solid metal heat sink, which uses the entire device to efficiently divert the heat throughout the core structure. This will ensure a stable high light output for a much longer period, and prolong the lifetime of the LED Chip.