It does not settle down and make its choice until it is measured. So a particle of matter could also be a wave of energy, and a radioactive atom may be decayed or it may be whole. Until we look, nothing is certain. Existing in one known, static condition requires no energy. But existing in two oscillating conditions simultaneously isn't so economical.
Energy is required.
Even a vacuum frozen to absolute zero will require energy. And a vacuum at absolute zero is a succinct description of most regions in outer space. Physicists have argued for decades whether spaceships could convert this energy. The motion of the pendulum, twisting one of the plates, could not be explained unless the zero-point was built into calculations. Russian researchers, in an attempt to make up for their lack of alien craft, tried bombarding water with sound to create air pockets which imploded, creating energy flashes.