The n‐type conductivity in commercially available stabilized zirconia electrolyte tubes was studied from 600° to 1400°C using three independent techniques: emf measurements on mixtures, coulometric titration of oxygen out of liquid silver or copper, and electrolyte breakdown in gas mixtures with low oxygen activities. From the coulometric titration results where is the oxygen pressure at which the ionic and n‐type conductivities are equal. Determinations of the electrolyte breakdown voltage permit reasonable estimates of to be made. Disagreement between the first two techniques was found which enabled discrepancies in the literature to be resolved.