The peak power is not always readily measurable, however, and the measurement of the average power P a v g is more commonly performed by an instrument. If one defines the energy per pulse as ε ε p u l s e = ∫ ∫ 0 T p ( t ) d t then the average power is P a v g = 1 T ∫ ∫ 0 T p ( t ) d t = ε ε p u l s e T .