Can Unchecked Power be used to deal 12 damage to all units at battlefields if your units are already exhausted?

Ruling: Yes, Unchecked Power can be used even if your units are already exhausted. Exhausting your units is an effect, not a cost, so you do as much as you can and then proceed to deal 12 damage to all units at battlefields.

Nuances:

• If exhausting were a cost (indicated by text like "exhaust all friendly units:" or "if you exhaust" or "you may exhaust then"), then you would not be able to deal the 12 damage if units were already exhausted
• Since it's just part of the effect, you simply do as much as possible and continue with the rest of the card's effect