Smoke & CO Detectors · Head to head

First Alert SC5 Hardwire Smart Smoke & CO Alarm vs Google Nest Protect (Battery)

Full Smart Smoke & CO Detectors comparison in 2026

Updated October 2026
Data from Amazon and 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.
Google Nest Protect (Battery)
Winner
Google Nest Protect (Battery)
$406.99

Last recorded price

Buy on Amazon USA
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.
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FeatureFirst Alert SC5 Hardwire Smart Smoke & CO AlarmGoogle Nest Protect (Battery)Winner
Rating3.54.4Google Nest Protect (Battery)
Warranty10 years2 yearsFirst Alert SC5 Hardwire Smart Smoke & CO Alarm
Connectivity2.4 GHz WiFi2.4 GHz WiFi, Bluetooth, OtherGoogle Nest Protect (Battery)
SensorsSmoke, COSmoke, CO, Occupancy, Temperature, Humidity, Ambient Light, MotionGoogle Nest Protect (Battery)
Built-in LightNOYESGoogle Nest Protect (Battery)
Tests ItselfNOYESGoogle Nest Protect (Battery)
PathlightNOYESGoogle Nest Protect (Battery)
IntegrationsGoogle HomeGoogle Home, Home AssistantTie
ScreenNONOTie
AlertsFire Alerts, CO Alerts, Low Battery AlertsFire Alerts, CO Alerts, Low Battery AlertsTie
Built-in SirenYESYESTie
Steam CheckYESYESTie

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

Winner
Google

Google Nest Protect (Battery)

Prime exclusive deal
$406.99

Last recorded price

Buy on Amazon USA
  • + 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.

Price history compared

Every price change of both, in the same store, so the gap between the two lines is what one costs more than the other.

  • First Alert SC5 Hardwire Smart Smoke & CO Alarm
  • Google Nest Protect (Battery)

Loading price history...

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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