Energy is another "currency" in Archlight. It is a personal value and can be used in many ways. You can pull up this window ingame by using the energy button on the top of your screen. This shows all the ways energy can be earned and spent.
Completing Tasks gives 5 energy.
Beds builds up energy over time, up to 480 for 24 h depending on bed tier.
Being Online gives 20 energy(30 if awakened) per two hour online - Cannot be xlogged
You can capture nodes, which increases your overall damage by 0.10% permanently and costs 25 energy. There are 100+ nodes in Archlight online, so expect to be getting atleast a 11.1% bonus damage if you collect them all. If you feel like you're not regenerating enough energy, then you should try Awakening, this will increase your energy regeneration. You can also buy guild energy regeneration perks to boost that even further.