Hello, I was wondering if this electrical service panel on the photo had the amp capacity of 100 amp? The sum of individual breakers is 205 amp and far exceeds 100 amp specified at the plate. Does this mean that some of the breakers are not used? Thanks, h.

It is a 100 amp box. The reason the breaker capacity is higher is the assumption that you will not have everything on at one time. 100 amps is rarely used in a home as a main panel today, 150 or 200 is most common.