The reopening will happen at 7 a.m. Saturday.
The hospital was temporarily closed after the power went out Tuesday, likely caused by a flood in the basement.
The outage prompted 120 patients to be evacuated and relocated to other facilities.
Power was restored by Wednesday morning, but only the E.R. was open to walk-up patients. Anyone who needed to be admitted had to be taken to another hospital.
"This swift reopening is a testament to the dedication, coordination, and rapid response of hundreds of Jefferson colleagues and partners who worked around-the-clock to maintain our patients' uninterrupted care," said Joseph G. Cacchione, MD, CEO of Jefferson, in a statement.