The Power Level of each equipped weapon and armor piece contribute to your Guardian’s [b]Effective Light Level.[/b] Your [b]Effective Light Level[/b] is determined by taking your [b]Average Equipment Power[/b] (the sum of the Power Level of your three equipped weapons and five equipped armor pieces divided by eight) then adding your [b]Seasonal Artifact Bonus[/b] levels: (W1 + W2 + W3 + A1 + A2 + A3 + A4 + A5) / 8 = AEP AEP + SAB = ELL This [b]ELL[/b] is used in a number of activities to affect the amount of damage the Guardian receives from or inflicts upon enemy Combatants or opposing Guardians. You will receive less damage from and deal more against a target which you have a higher [b]ELL[/b] than, with these bonuses maxing out at a difference of (iirc) 20 levels. On the flip side you will receive [i]more[/i] damage from and deal [i]less[/i] damage against a target which you have a lower [b]ELL[/b] than with these penalties maxing out at a difference of (again iirc) 50 levels, with the added wrinkle that any PvE enemy Combatant with a Power Level 50 levels greater than your [b]ELL[/b] will be entirely [u]immune[/u] to any damage you attempt to cause it via weapons, abilities or vehicles. It should be noted that a number of PvP modes have Light Levels disabled entirely to create a more level playing field. In addition there are a variety of PvE activities that will place a cap on the Guardians’ maximum [b]ELL[/b] as a means to increase difficulty. (΄◉◞౪◟◉｀)

Power on a weapon is relevant to its damage but not as much as the perks unless its a big power difference For example an 1810 will do slightly more than an 1800, but 1800/1810 will do significantly more than a 1600 of the same gun