Besides producing hydrogen from surplus renewables, electrolyzers can also provide grid ancillary services like enhancing the stability, resilience, and robustness of the power grid. The paper presents a novel electrical circuit model for a proton exchange membrane electrolyzer (PEMEL) that has been validated using experimental data from a 400W electrolyzer. To demonstrate its adaptive capability, the proposed 400W electrical model is scaled up to a 1 MW stack, and this system is validated by comparison to another report of 1 MW stack experimental results. Results show that the developed model reproduces very similar step responses to those reported for the 400W electrolyzer and 1 MW stack. In this paper, the developed model was then used to evaluate the grid frequency response against disturbance, possible resilience advantages from frequency control services, and frequency sensitivity analysis for a modified IEEE-13-bus-distribution-feeder system. These simulations indicate that PEMEL responds to frequency changes faster than traditional synchronous generators, indicating that using the proposed PEMEL stack has a high potential for improving frequency stability, resilience, and robustness.