Every card like mt coronet aka super rod, special charge and energy recycler, you can play them if you have less than the number of energys or pokemon that are stated you can retrieve from the discard (not if there are 0, you always have to have a target). However, there are also cards that state up to (insert number here) energy. With those cards you do have to have at least 1 energy in the discard but you do not have to get more than 1 if you don’t want to.