Properly designed, calibrated, and operated weighing lysimeters are recognized as accurate tools for measuring changes of soil water storage (ΔS) in the soil profile contained in the lysimeter. The neutron probe, NP, also is recognized as an accurate tool for determining soil profile water storage, S, and ΔS over the depth range of the neutron probe readings, again when properly calibrated and operated. Both methods have been used to calculate evapotranspiration (ET) using the soil water balance equation (ET = ΔS + I + P + R + F) applied to a control volume, where I is irrigation, P is precipitation, R is the sum of runon and runoff, and F is flux into or out of the control volume. However, weighing lysimeters are expensive to install and operate and are not portable, and the neutron probe faces regulatory pressures and cannot be used unattended, limiting its use. Past attempts to use electromagnetic soil water sensors based on capacitance principles to accurately determine profile water content have not met with success. Recent advances in soil water senor technology have led to accurate, low power, and relatively inexpensive electronic soil water sensors based on time domain reflectometry (TDR) theory, which can be installed in situ. Assuming that accurate values or controls were available for I, P, R, and F, we concentrated on evaluating S and ΔS as determined by lysimeter, NP, and TDR sensors. Over a cropping season at Bushland, Texas, USA we compared S and ΔS in a 2.3-m deep profile of silty clay loam soil as assessed by a large, precision weighing lysimeter, the NP in two access tubes in the lysimeter, and three profiles of TDR soil water sensors installed in the lysimeter, each profile consisting of 15 sensors. Weighing lysimeter mass was recorded every 5 minutes and TDR sensors were read every 15 minutes, both automatically using dataloggers, while the neutron probe readings were done manually at approximately one-week intervals. Comparing TDR sensors with neutron probe, coefficients of determination for profile water content and for ΔS were 0.97 and 0.91, respectively, when one-week intervals were considered. Coefficients of determination for comparisons of TDR sensors to lysimeter were 0.95 for S and 0.92 for ΔS, while values for comparison of neutron probe to lysimeter were 0.91 for water storage and 0.83 for ΔS, again for one-week intervals. Poorer performance of the NP was likely due to the fact that it could not be read to depths greater than 1.90 m, which limited the profile sensed to the top 2.0 m of soil.