Soprano pipistrelles exhibit considerable plasticity in both the structure and rate of echolocation call production. In search phase in the laboratory, calls are produced either as a single pulse per wingbeat cycle, or as double pulses. The amplitude of double pulses is reduced compared to the preceding single pulse. The energy flux density of either pulse of a double pulse per wingbeat was lower than a single pulse per wingbeat, and is achieved by a combination of reduction in both duration and amplitude. The combined energy of the double pulses is not significantly greater than the single pulse which precedes it. The decision to produce a double pulse may be an indication of the bat requiring additional information from the target. The production of double pulses per wingbeat may serve to achieve a higher rate of information flow for no significant increase in energetic expenditure when a possible target is detected. The proposal that echolocation during flight comes for free as a by-product of the intimate coupling among wingbeat, respiration, and echolocation is discussed.