 Additional advantages include long-term stability, fuel flexibility, low emissions, and low operating costs.However, the greatest disadvantage is the high operating temperature, which results in long start-up times and break-in times.The high operating temperature also leads to mechanical compatibility issues such as thermal expansion mismatch and chemical stability issues such as diffusion between layers of material in the cell

In principle, the process of any fuel cell could be reversed, due to the inherent reversibility of chemical reactions.