Building integration using thin-film flexible photovoltaic (PV) cells with load-carrying structures requires understanding of their electrical performance under continuous mechanical loadings. Limited results mainly focus on the electrical performance of PV cells under certain fixed mechanical strains. In this paper, an approach is examined to continuously apply tensile strains on PV cell specimens; therefore the short circuit current (I-SC) and open circuit voltage (V-OC) are constantly monitored. Two types of PV cells are studied under the proposed approach including amorphous silicon (a-Si) and organic PV cells and the results demonstrate its practicability to determine the critical tensile strains reliably for both PV types. It is found that V-OC is more sensitive than I-SC to the applied tensile strain for both types of PV cells and substantial degradation in Voc for a-Si cells initiates at the tensile strain of 1.51%. For organic cells, significant reduction in V-OC is observed at the critical tensile strain of 1.46% in association with yielding of the substrate. While noticeable degradation can be only observed in I-SC from 1.67% strain for a-Si PV cells and from 3.09% strain for organic ones. In addition, linear declines with temperature in Voc of both PV types are quantified for temperatures over 30 degrees C.