But expert say homes need a lot more smoke alarms than that. How Many Smoke Alarms Are Needed in a HomeThe cut-to-the-chase answer to this question is that you’re probably going to need five or more alarms in your residence. Battery-Operated vs. Hardwired Smoke AlarmsHardwired smoke alarms, where the alarm is powered by a home’s electrical wiring, are generally preferred by fire experts over battery-operated alarms. While smoke alarms and smoke detectors are terms often used interchangeably, they’re technically different products. While it’s possible a manufacturer might refer to a single smoke alarm with a built-in alert as a smoke detector, the correct term is smoke alarm.