It happened at the Oxford Terrace apartments on the 300 block of Market Street in Oxford Borough.
Tenants stayed in a shelter until about 2:15 this morning, when they were allowed to return to their homes.
Officials say, a delivery truck knocked out power to the senior living center, when it hit a transformer Wednesday afternoon.
The Red Cross helped about 40 people, providing food and a place to wait, until the power was restored..
