Plants differ in their ability to withstand freezing temperatures, even within a given species. Knowledge of cold tolerance allows for deployment of planting stock in appropriate climates. This is especially important for breeding programs for disease resistance and crop improvement where progenitors may be adapted to different climates, as well as selecting populations for assisted migration. Relative electrolyte leakage (REL) has been used for decades to provide a laboratory assessment of the degree of injury caused by exposure to freezing temperatures. Replicates of tissue are exposed to increasingly cold temperatures in a test chamber and sequentially removed at specific minimum temperatures. When cells freeze and rupture, electrolytes are released and are detectable in solution with a conductivity meter. Electrolyte leakage at specific minimum temperatures is relativized to maximum leakage from total cell lyses caused by freezing in liquid nitrogen, boiling, autoclaving or heating to dryness. The temperature where 50% leakage has occurred (Tm50) and cellular repair is unlikely is frequently used to quantify REL results and compare cold tolerance between groups. Currently here are few commercially available options for rapid measures of electrical conductivity in liquid samples. I developed a high throughput relative electrolyte (HTREL) system to multiplex sequential measurements of electrical conductivity of plant tissue samples in solution via a bridge circuit. The conductivity bridge measures 96 electrode pairs in a few seconds compared to over an hour for manual measurements with handheld conductivity meter. The high throughput nature of this equipment is essential to making the thousands of observations necessary to build robust relative electrolyte leakage curves. The conductivity bridge was designed to be used with large volume, disposable well plates (3.5 ml per well) and constructed at the University of Vermont Instrument Manufacturing Facility in Burlington Vermont. A Campbell Scientific Inc. (Logan, Utah) data logger connected to several multiplexers sequentially moves through the 96 electrode pairs and measures electrical conductivity in a few seconds and records the results. Complementary to the hardware developments are R based programs to calibrate the electrodes to standard solutions and create the temperature response curves . The hardware design and R code will be published with an open source license and made freely available to enable wider adoption of the REL technique and advance research into climate suitability of plant populations.