ABSTRACT Phureja Group potato is endemic and important for northern Andean countries such as Colombia, Ecuador and Venezuela, where it is grown over a wide range of elevation. The objective of the study was to compare the biomass accumulation of five potato cultivars in three contrasting environments in elevation from a latent response variable of vector nature, analogous to “heat efficiency index”. Destructive samplings were carried to obtain biomass. A biomass accumulation model was proposed using a latent response variable that integrates total biomass per plant with thermal time, analogous to the “heat use efficiency index”. The proposed latent response variable allowed measuring the efficiency in biomass accumulation and making comparisons between elevations and cultivars, with a nonparametric longitudinal variance analysis. The middle location was where the highest efficiency in accumulation of total biomass was observed. The accumulation of total biomass was slow at the higher elevation location during the vegetative stage, but it increased considerably after the initiation of the growth of tubers. The study showed a clear genotype-environment interaction, suggesting that biomass accumulation changes with elevation according to the cultivar. The methodology used in this study has the potential to be used in the longitudinal comparison of cultivars and environments, even when variations in elevation or temperature alter the length of growing cycles.