Even if you don't have a fire in your home, you can be suffocated by carbon monoxide. A good detector should also protect you against this. Hardwired vs. Battery powered. If your home has hardwired alarms, they will all be interconnected, so that if one goes off, they all will go off. Hardwired alarms also receive their power from your home, and only use batteries as backups. Standalone detectors run on batteries alone, so they may need to be replaced more often, and cannot signal each other in the event of an emergency Nest's and OneLink's alarms are an exception to this. However, it's a lot easier to mount standalone smoke detectors where you need them. Today's best Nest Protect deals?$115. 99View$119View$127. 65ViewLow Stock$127.