One of the residents smelled smoke and alerted the other tenants of the home at 583 Madison St., fire investigator Jeff Taylor said.
Firefighters from Napa and Cal Fire responded at 12:18 a.m.
The two-alarm fire is believed to have been sparked by a cigarette left on the front porch, Taylor said. It was controlled within 30 minutes, and there were no injuries.
Firefighters had to avoid a fallen power line that was arcing in front of the house when they arrived, Taylor said. They were at the scene until about 4:45 a.m.