Renewable energy sources (RES) will play an important role in decarbonizing the electricity grid. However, high penetration of RES introduce new challenges to electrical power systems due to the variable and intermittent nature of energy production. Energy storage and flexible loads are ancillary services that can introduce reliability and resiliency to the electricity grid on a local scale. In this context, electrolysers have the potential to provide both energy storage and flexible loads through the production and storage of hydrogen. Moreover, hydrogen is considered an attractive and versatile alternative energy carrier due to its high calorific value and low environmental impact and it also can be exported as fuel to different markets. Although electrolysers are an interesting option to provide ancillary services, batteries also have the potential to compete in the new system services market as a clean alternative for energy storage and balancing services. Thus, the current report aims to review the capability of electrolysers, most notably Proton Exchange Membrane Electrolysers (PEME) and Alkaline Electrolysers (ALKE), to operate under variable conditions and to provide system services in Ireland. Furthermore, a technical-economic comparison of the potential of electrolysers and batteries to provide system services is presented.