The ClimaVUE™50 does need to be powered continuously to make the routine wind measurements (every 10 seconds) that are combined to give the wind speed and direction. If you only power up and quickly grab a measurement, those wind speed and direction measurements will be of little value, given the inherently variable nature of wind. Campbell Scientific highly recommends that you power the ClimaVUE™50 instruments continuously for reliable wind measurement. The average current drain for the ClimaVUE™50 during the quiescent state and routine 10 s wind measurement is on the order of 300 microAmps, so battery drain from continuous power should be minimal.