As a simple example, burning one kilogram of coal releases more energy than detonating a kilogram of TNT, but because the TNT reaction releases energy more quickly, it delivers more power than the coal. If Δ W is the amount of work performed during a period of time of duration Δ t, the average power P avg over that period is given by the formula P a v g = Δ Δ W Δ Δ t . It is the average amount of work done or energy converted per unit of time. Average power is often called "power" when the context makes it clear.