Two fire engines from Worthing were called to reports of a fire beneath the stairs in a property in Rectory Farm Road, Sompting, in the early hours of Friday (January 26).
The crews arrived on the scene within six minutes, where they were confronted with a well-developed fire in the lounge with smoke issuing from both floors, the spokesman said.
Fortunately, the occupiers had evacuated the building.
Four firefighters wearing breathing apparatus entered the house and extinguished the fire using jets and hose reels.
The fire was believed to have started in the electrical consumer unit under the stairs and caused extensive damage throughout the property, the spokesman said.
Darren Wickings, watch commander, said: “This incident highlights how important working smoke alarms are.
“The occupiers were alerted by flickering lights and a noise downstairs.
“Luckily one of them was just going to bed and went to investigate.
“If it had been half an hour later, the outcome could have been extremely different.
“We urge everyone to check they have working smoke alarms and test them today.
“Smoke alarms really can be the difference between life and death in a fire situation.”