Well, power has a specific definition, and there are ways to observe that do not transfer power - but all influence the system itself. Energy is the ability to do work. Power is a measure of how much energy is released in a given time. For example, a kilowatt-hour is a unit of energy. With a kilowatt-hour you can lift a metric ton about 350 meters into the air. A kilowatt is a unit of power. With a kilowatt, you can lift a metric ton at a speed of about .3 feet per second.