How much energy does Phantom Barrage restore?

The refund scales with stacks, so build up fire on the target before you fire it off.

Cast it into a target carrying only a stack or two and you get a small top-up. Cast it after your team has piled fire debuffs on and it becomes a real refill. The 37 cap means stacking only pays off up to a point. Once the target carries enough fire to hit the cap, more stacks add nothing to this skill's return.

EP comes from one pool shared by the whole party, so what Phantom Barrage gives back is not kept for the Aniimo that cast it. It pays for the next skill from whichever Aniimo you swap in. For scale, Mellobloom's Thorny Blessing costs 30 EP and Wind Bomb Rush costs 45 EP before its upgrade, so a capped Phantom Barrage covers a big chunk of an expensive skill.

Fire stacks pay out twice against overflowing Alphas

Fire debuff stacks also feed energy when you fight an Alpha in the Anomaly Spark overflowing state. There, each additional fire stack makes the Alpha drop an energy orb that restores EP. A team that keeps fire stacked on an overflowing Alpha collects those orbs and then gets a bigger Phantom Barrage refund on top.

Not settled: The per-stack figure is approximate. About four energy per stack is the observed rate, but the exact value per stack, and the number of stacks it takes to reach the 37 cap, are not pinned down.