Live Fast

If an effect says you get one or more energy , you get that many energy counters. To pay one or more energy , you lose that many energy counters. You can't pay more energy counters than you have. Any effects that interact with counters a player gets, has, or loses can interact with energy counters.

If a spell or ability with one or more targets states that you "may pay" some amount of energy , and each permanent that it targets has become an illegal target, the spell or ability won't resolve. You can't pay any energy even if you want to.

energy is the energy symbol. It represents one energy counter.