Quantum metrology triangle experiments combine three quantum electrical effects (the Josephson effect, the quantum Hall effect and the single-electron transport effect) used in metrology. These experiments allow important fundamental consistency tests on the validity of commonly assumed relations between fundamental constants of nature and the quantum electrical effects. This paper reviews the history, results and the present status and perspectives of quantum metrology triangle experiments. It also reflects on the possible implications of results for the knowledge on fundamental constants and the quantum electrical effects. In terms of relative standard uncertainty, the best result currently achieved is nine parts in 107, while the goal is to reduce the uncertainty down to below five parts in 107 in order to provide an impact on the adjustment of the physical constants’ values.