org-agenda-columns-add-appointments-to-effort-sum

org-agenda-columns-add-appointments-to-effort-sum is a variable defined in `org-agenda.el'.
Its value is

nil

Documentation:
Non-nil means the duration of an appointment will add to day effort.
The property to which appointment durations will be added is the one given
in the option `org-effort-property'. If an appointment does not have
an end time, `org-agenda-default-appointment-duration' will be used. If that
is not set, an appointment without end time will not contribute to the time
estimate.

You can customize this variable.