First Alert SC5 Review: A Battery-Powered Successor to the Discontinued Nest Protect
A Wi-Fi smoke and CO alarm built to slot into old Nest Protect mounts and the Google Home app, with a few false-alarm and battery gripes to weigh first.
The First Alert SC5 is aimed squarely at households whose Google Nest Protect alarms are aging out or already discontinued: it reuses the same wall mount, links into the same Google Home app, and covers both smoke and carbon monoxide from six CR123A batteries. Buyers consistently praise the easy swap-in setup and loud, voice-guided siren, but a recurring share report nuisance false alarms, a required extra app step before Google Home linking, and the loss of the Nest Protect's pathlight. It is a reasonable, well-integrated pick for Google Home households replacing Nest hardware, less compelling if you want Alexa, HomeKit, or Matter support.
- Nest Protect replacements
- Google Home households
- Battery-only installs
- Multi-room interconnected coverage
Pros
- Purpose-built drop-in replacement for the discontinued Nest Protect, including compatible wall mounts
- Google Home integration lets new SC5 units and older Nest Protect alarms live in one app
- Loud built-in siren with voice alerts that announce the type and location of the hazard
- Combined smoke and CO detection with low-battery alerts to avoid late-night chirps
- 10-year warranty reflecting long-term build confidence
Cons
- No Alexa, Apple HomeKit, SmartThings, or Matter support, Wi-Fi is the only connectivity path
- No pathlight, a feature many reviewers specifically missed from the Nest Protect
- Requires setup in the separate First Alert app before it can link into Google Home
- Runs on six CR123A batteries rather than common AA cells
- A recurring share of reviewers reported false alarms, and a few saw batteries drain faster than the rated life
Who is the First Alert SC5 for?
The SC5 was built as the official replacement for Google's discontinued Nest Protect, and that is exactly how most owners use it: dropping a new SC5 onto an existing Nest wall plate and bringing it into the same Google Home app alongside any Nest Protect units still in service. It runs entirely on batteries (six CR123A cells, no wired option), connects over 2.4GHz Wi-Fi, and combines a photoelectric smoke sensor with an electrochemical carbon monoxide sensor in one unit. It suits homes already inside the Google ecosystem more than households looking for Alexa or Apple HomeKit control.
What buyers love
The most repeated praise is how straightforward the migration from Nest Protect is: the SC5 fits existing Nest backplates and, once paired through the First Alert app, shows up in Google Home next to older units so the whole house stays under one dashboard. Reviewers also call out the loud built-in siren with voice alerts that announce the type and location of a hazard, plus mobile push notifications for smoke, carbon monoxide, and low battery, which several owners say means no more late-night low-battery chirps. Some also credit the steam-check tuning for cutting down nuisance alerts from cooking or showers compared to a basic alarm.
What to know before you buy
Connectivity tops out at 2.4GHz Wi-Fi only, with no Alexa, Apple HomeKit, SmartThings, or Matter support, so it fits best in a Google-first smart home. Setup also requires registering the alarm in the separate First Alert app before it can be linked into Google Home, an extra step several reviewers found clunky compared to the old Nest app. The pathlight that lit hallways on the Nest Protect is gone entirely, which multiple owners specifically miss. A recurring complaint is false alarms cropping up weeks or months after install, and a smaller group of reviewers reported having to swap batteries well before the rated life, so it is worth budgeting for occasional battery changes even though the unit is rated for a decade.
Is the First Alert SC5 worth it?
Between a long warranty, dual smoke and CO sensing, and a design purpose-built to inherit an existing Nest setup, the SC5 lands as a solid if imperfect successor rather than a clear upgrade. Feedback skews toward strong satisfaction from buyers who just needed a drop-in Nest Protect replacement inside Google Home, while the false-alarm and missing-pathlight complaints pull down the experience for others. It is a sensible buy if you are already committed to Google Home and want interconnected smoke and CO coverage without rewiring anything, less so if you want a smart alarm that plays nicely across Alexa, HomeKit, or other ecosystems.
Frequently asked questions
Does the First Alert SC5 replace a Google Nest Protect alarm?
Yes, the SC5 is designed as the official replacement for Google's discontinued Nest Protect. It fits existing Nest wall mounts and, once set up through the First Alert app, can be added into the same Google Home app as any remaining Nest Protect units.
Does the First Alert SC5 work with Alexa or Apple HomeKit?
No. The SC5 connects only over 2.4GHz Wi-Fi and integrates with Google Home; it does not support Alexa, Apple HomeKit, Samsung SmartThings, Home Assistant, IFTTT, or Matter.
Is the First Alert SC5 battery-powered or wired?
It is battery-only, powered by six CR123A batteries rated for up to 10 years, with no hardwired power option.
Does the First Alert SC5 detect both smoke and carbon monoxide?
Yes. It uses a photoelectric sensor for smoke, which is generally more sensitive to smoldering fires, and an electrochemical sensor for carbon monoxide, plus a built-in siren and voice alerts for both hazards.
Does the First Alert SC5 have a pathlight like the Nest Protect?
No, it does not include a pathlight or nightlight feature. This is a commonly noted gap for buyers coming from the Nest Protect, which had one.
Does the First Alert SC5 reduce false alarms from cooking or steam?
It includes steam-check detection technology intended to better distinguish cooking smoke or shower steam from an actual fire. Most reviewers find it effective, though a portion of buyers still report occasional false alarms.
