The pressure and temperature dependency of the electrical conductivity of poly(vinyl alcohol)/poly(vinyl pyrrolidone) (1/1, w/w) and poly(vinyl alcohol) and composites with dispersed nano-graphene platelets were studied. Above the critical platelet fraction for electric charge percolation, the composites function as pressure-induced electro-switches. The conductor to insulator transition is optimally intense and stable. The electrical conductivity drops by two orders of magnitude at a critical pressure around 750 bars. The transition is stable over tenths of degrees above room temperature. The reduction of the conductivity upon pressure results from the competition between the pressure dependencies of the polarizability of the polymer matrix and the inter-platelet separation, respectively. Both contributions control the fluctuation induced tunneling of electrons through the polymer barrier separating adjusting conductive platelets. The role of the local electric field at the polymer-platelet interfaces by assisting tunneling is suppressed by the decrease of the polarizability upon pressure.