Decarbonization of ammonia production has been a matter of interest in the recent years. A sustainable Power-to-Ammonia opportunity is through the electrolysis of water or steam for hydrogen production instead of the current SMR. This study is framed within the H2GIGA flagship project, specifically in the scale-up project AEL4GW, and addresses the production of green ammonia via the electrolysis of water and steam through alkaline and solid oxide electrolyzer coupled with a Haber-Bosch process. A conceptual design is simulated for 100 MW electrolysis plant and assessed.