Winner
Data from the official First Alert site.
2026 verdict
One runs on batteries, the other on your home's wiring, and the First Alert SC5 Battery Smart Smoke & CO Alarm edges this matchup on owner sentiment.
The two are otherwise the same alarm: both combine photoelectric smoke and electrochemical carbon monoxide sensing, 85 dB voice alerts, steam-check nuisance reduction, 2.4 GHz Wi-Fi and Google Home, and neither supports Alexa, Apple HomeKit, SmartThings or Matter. The First Alert SC5 Hardwire Smart Smoke & CO Alarm swaps the battery-only design for mains power and a lithium backup, so it never needs a battery change but needs an existing wired circuit. Choose the battery version to place alarms anywhere without wiring, and the hardwire version if you are replacing existing wired alarms and want power plus backup.
Works with
Connectivity
- Wi-Fi 2.4 GHz
vs
Works with
Connectivity
- Wi-Fi 2.4 GHz
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| Feature | First Alert SC5 Battery Smart Smoke & CO Alarm | First Alert SC5 Hardwire Smart Smoke & CO Alarm | Winner |
|---|---|---|---|
| Rating | 3.6 | 3.4 | First Alert SC5 Battery Smart Smoke & CO Alarm |
| Warranty | 10 years | 10 years | Tie |
| Connectivity | 2.4 GHz WiFi | 2.4 GHz WiFi | Tie |
| Integrations | Google Home | Google Home | Tie |
| Screen | NO | NO | Tie |
| Sensors | Smoke, CO | Smoke, CO | Tie |
| Alerts | Fire Alerts, CO Alerts, Low Battery Alerts | Fire Alerts, CO Alerts, Low Battery Alerts | Tie |
| Built-in Siren | YES | YES | Tie |
| Built-in Light | NO | NO | Tie |
| Tests Itself | NO | NO | Tie |
| Pathlight | NO | NO | Tie |
| Steam Check | YES | YES | Tie |
What the differences mean
Power source
The First Alert SC5 Battery Smart Smoke & CO Alarm runs on six CR123A batteries rated for up to 10 years. The First Alert SC5 Hardwire Smart Smoke & CO Alarm runs on mains power with a 3V lithium battery kept only as backup.
Placement vs installation
The battery version goes anywhere in the house with no wiring and suits rentals. The hardwire version needs an existing alarm circuit but in return never asks you to change a battery.
Power outages
The hardwire version keeps running on its backup battery when the mains fails, where the battery version is unaffected by wiring at all. Both keep protecting through an outage.
Everything else
The sensors, 85 dB voice alerts, steam-check reduction, 2.4 GHz Wi-Fi, Google Home integration and 10-year warranty are identical, so the pair really comes down to whether you have wiring.
Which one to buy if
- you have no existing alarm wiring
The First Alert SC5 Battery Smart Smoke & CO Alarm installs anywhere with no electrical work.
- you are replacing existing hardwired alarms
The First Alert SC5 Hardwire Smart Smoke & CO Alarm uses mains power with a lithium backup and needs no battery changes.
- you rent and cannot modify the wiring
A battery-only alarm is the only option that leaves the wiring untouched.
- you want the end-of-life warning with mains reliability
The hardwire model pairs mains power with a backup and reports its end-of-life the same way.
Winner
- + Rating: 3.6
- - Rating: 3.4 vs 3.6
What owners say
Owners of the First Alert SC5 Battery Smart Smoke & CO Alarm and the First Alert SC5 Hardwire Smart Smoke & CO Alarm describe the same experience, since the sensing, siren and app are shared. Both groups praise the loud, voice-guided siren that names the type and location of danger, the migration from a Nest Protect, and the end of late-night low-battery chirps now that warnings arrive in the app. The shared gripes are the missing pathlight, the extra step of registering each unit in the First Alert app before it links to Google Home, and a recurring share of nuisance false alarms; the battery model additionally draws complaints from a few owners whose cells drained faster than the rated life.
Frequently Asked Questions
Which is better overall: First Alert SC5 Battery Smart Smoke & CO Alarm or First Alert SC5 Hardwire Smart Smoke & CO Alarm?
They are the same alarm on different power. Pick the First Alert SC5 Battery Smart Smoke & CO Alarm if you have no wiring, and the First Alert SC5 Hardwire Smart Smoke & CO Alarm if you are replacing existing wired alarms and want no battery changes.
What is the difference between the First Alert SC5 battery and hardwired versions?
Power only. The battery model uses six CR123A cells for up to 10 years, while the hardwired model runs on mains power with a lithium backup battery. The sensing, alerts, app and warranty are the same.
Does the First Alert SC5 require a subscription?
No. Both the First Alert SC5 Battery Smart Smoke & CO Alarm and the First Alert SC5 Hardwire Smart Smoke & CO Alarm send their alerts through the free First Alert app and Google Home, with no monthly fee.
Do the First Alert SC5 models work with Alexa, Apple HomeKit or Matter?
No. Both the First Alert SC5 Battery Smart Smoke & CO Alarm and the First Alert SC5 Hardwire Smart Smoke & CO Alarm connect over 2.4 GHz Wi-Fi and integrate with Google Home only. Alexa, Apple HomeKit, SmartThings and Matter are not supported.
Do the SC5 alarms reduce false alarms from cooking?
Both include steam-check detection intended to tell cooking smoke or shower steam from a real fire. Most owners find it effective, though a portion still report occasional nuisance alarms.
Who should buy the First Alert SC5 Hardwire Smart Smoke & CO Alarm?
Homeowners replacing existing hardwired smoke alarms who want mains power with a battery backup and a 10-year warranty, and who do not mind relying on Google Home.
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