Data from the official First Alert and Google sites.
2026 verdict
One is hardwired, the other runs on batteries, and the Google Nest Protect (Battery) takes this matchup on features and owner sentiment.
It detects smoke and carbon monoxide and adds occupancy, temperature, humidity, ambient-light and motion sensing, an automatic pathlight and a monthly self-test that the First Alert SC5 Hardwire Smart Smoke & CO Alarm does not carry, and it works with Google Home and Home Assistant. The First Alert SC5 Hardwire Smart Smoke & CO Alarm answers with the lower price and a longer 10-year warranty against 2 years, plus mains power with a battery backup so it never needs a battery change. Both interconnect and voice an early warning. Pick the Google Nest Protect (Battery) for the smart sensing and a wireless install, and the First Alert SC5 Hardwire Smart Smoke & CO Alarm if you have existing alarm wiring and want value.
Works with
Connectivity
- Wi-Fi 2.4 GHz
vs
Winner
Price unavailable right now
Works with
Connectivity
- Wi-Fi 2.4 GHz
- Bluetooth
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| Feature | First Alert SC5 Hardwire Smart Smoke & CO Alarm | Google Nest Protect (Battery) | Winner |
|---|---|---|---|
| Rating | 3.4 | 4.4 | Google Nest Protect (Battery) |
| Warranty | 10 years | 2 years | First Alert SC5 Hardwire Smart Smoke & CO Alarm |
| Connectivity | 2.4 GHz WiFi | 2.4 GHz WiFi, Bluetooth, Other | Google Nest Protect (Battery) |
| Sensors | Smoke, CO | Smoke, CO, Occupancy, Temperature, Humidity, Ambient Light, Motion | Google Nest Protect (Battery) |
| Built-in Light | NO | YES | Google Nest Protect (Battery) |
| Tests Itself | NO | YES | Google Nest Protect (Battery) |
| Pathlight | NO | YES | Google Nest Protect (Battery) |
| Integrations | Google Home | Google Home, Home Assistant | Tie |
| Screen | NO | NO | Tie |
| Alerts | Fire Alerts, CO Alerts, Low Battery Alerts | Fire Alerts, CO Alerts, Low Battery Alerts | Tie |
| Built-in Siren | YES | YES | Tie |
| Steam Check | YES | YES | Tie |
What the differences mean
Power
The First Alert SC5 Hardwire Smart Smoke & CO Alarm runs on mains power with a lithium backup. The Google Nest Protect (Battery) runs entirely on six lithium AA batteries, so it goes anywhere but needs periodic replacement.
Sensors
The Google Nest Protect (Battery) adds occupancy, temperature, humidity, ambient-light and motion sensing. The First Alert SC5 Hardwire Smart Smoke & CO Alarm senses smoke and carbon monoxide only.
Pathlight and self-test
Only the Google Nest Protect (Battery) has a night pathlight and a self-test that emails a monthly report. The First Alert SC5 Hardwire Smart Smoke & CO Alarm has neither.
Warranty
Ten years on the First Alert SC5 Hardwire Smart Smoke & CO Alarm against two on the Google Nest Protect (Battery).
Home Assistant
The Google Nest Protect (Battery) works in Home Assistant through a community integration, one more path than the First Alert SC5 Hardwire Smart Smoke & CO Alarm, which stops at Google Home.
Price
The First Alert SC5 Hardwire Smart Smoke & CO Alarm is the lower priced of the two and is still in production, while the discontinued Google Nest Protect (Battery) is limited to remaining stock.
Which one to buy if
- you have existing alarm wiring
The First Alert SC5 Hardwire Smart Smoke & CO Alarm uses mains power with a battery backup and needs no battery changes.
- you have no wiring and want batteries
The Google Nest Protect (Battery) installs anywhere on six AA batteries.
- you want a night pathlight
Only the Google Nest Protect (Battery) lights your way when you walk under it at night.
- you want the longest warranty and lower price
The First Alert SC5 Hardwire Smart Smoke & CO Alarm carries 10 years of cover for less.
- you want self-testing with a monthly report
The Google Nest Protect (Battery) checks its sensors continuously and reports monthly.
- + Warranty: 10 years
- - Rating: 3.4 vs 4.4
- - Connectivity: 2.4 GHz WiFi vs 2.4 GHz WiFi, Bluetooth, Other
Winner
Price unavailable right now
- + Rating: 4.4
- + Connectivity: 2.4 GHz WiFi, Bluetooth, Other
- + Sensors: Smoke, CO, Occupancy, Temperature, Humidity, Ambient Light, Motion
- - Warranty: 2 years vs 10 years
What owners say
Owners of both alarms agree on the core promise: app alerts, self-monitoring and a spoken warning that names the room are what separate them from a basic detector. Google Nest Protect (Battery) owners single out the early spoken warning and the monthly self-test email, and describe phone alerts catching real incidents while away; their complaints are the fixed 10-year life, expensive specific lithium batteries, old stock, and no Alexa or HomeKit. First Alert SC5 Hardwire Smart Smoke & CO Alarm owners single out how cleanly it drops into an existing wired or Nest mount with the included adapter, but miss the pathlight, find the First Alert app fussier and report the occasional false alarm.
Frequently Asked Questions
Which is better overall: First Alert SC5 Hardwire Smart Smoke & CO Alarm or Google Nest Protect (Battery)?
The Google Nest Protect (Battery) on features and owner sentiment, with extra sensors, a pathlight and self-testing. The First Alert SC5 Hardwire Smart Smoke & CO Alarm wins on price, warranty and being a current production hardwired option.
What is the biggest difference between the First Alert SC5 Hardwire Smart Smoke & CO Alarm and the Google Nest Protect (Battery)?
Power and sensing. The First Alert SC5 Hardwire Smart Smoke & CO Alarm is hardwired with a backup, while the Google Nest Protect (Battery) is battery-only and adds occupancy, temperature, humidity, light and motion sensors plus a pathlight.
Do the First Alert SC5 Hardwire Smart Smoke & CO Alarm and the Google Nest Protect (Battery) work with Google Home?
Yes, both work with Google Home. The Google Nest Protect (Battery) also works with Home Assistant. Neither supports Alexa, Apple HomeKit, SmartThings or Matter.
Does the Google Nest Protect (Battery) need special batteries?
Yes. It requires six Energizer Ultimate Lithium AA cells, not alkaline or rechargeable, which owners note are pricey. The First Alert SC5 Hardwire Smart Smoke & CO Alarm uses a lithium backup battery instead of replaceable cells.
Which has a longer warranty, the First Alert SC5 Hardwire Smart Smoke & CO Alarm or the Google Nest Protect (Battery)?
The First Alert SC5 Hardwire Smart Smoke & CO Alarm, at 10 years against 2 years on the Google Nest Protect (Battery).
Who should buy the First Alert SC5 Hardwire Smart Smoke & CO Alarm?
Homeowners with existing hardwired alarms who want mains power with a backup, a long warranty and a lower price, and who do not need the extra sensors or pathlight.
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