If you touch the following objects on the corresponding floor you will get one extra energy.
The house elf
The blank painting on the far left.
Lower Floor West:
Fire lamp on the right side of the great hall doorway.
Lower Floor West (2):
Central soldier statue.
Brown stick, in between Whomping Willow and Hagrids Hut.
Oranges painting (Next to Gryffindor's CR)
Lower Floors East:
He stack of books on the bench.
Peeves behind the stairs.
Person standing in alley between buildings.