ATP (adenosine triphosphate) stores more energy than ADP (adenosine diphosphate).

ATP has three phosphate groups with high energy bonds located between each group.

ADP has only two phosphate groups. ADP also has high energy bonds located between each group.

The presence of the third phosphate group and the additional high-energy bond between the second and third phosphate group in ATP enables it to store more energy than ADP, which does not have that third high-energy bond.