First Alert SC5 Review: The Smart Smoke & CO Alarm Built to Replace Your Nest Protect
A hardwired smoke and carbon monoxide alarm engineered as a drop-in swap for the discontinued Nest Protect, easy to install but missing its signature pathway night light.
The First Alert SC5 is a hardwired smoke and carbon monoxide alarm purpose-built to slot into the mounting plate left behind by the discontinued Google Nest Protect, wiring adapter included, so the swap is straightforward for anyone comfortable with basic DIY. It pairs with the Google Home app for mobile alerts, clearly differentiates between smoke and CO danger with voice announcements, and backs up its hardwired power with a lithium battery for outages. The most common trade-off owners flag is the lack of the motion-activated night light and pathway lighting the Nest Protect offered, along with an app experience some feel is less polished than Nest's. For Google Home households that need a reliable, code-compliant hardwired alarm rather than a multi-ecosystem smart hub, it is a sound long-term pick backed by a lengthy warranty.
- Nest Protect replacement seekers
- Google Home households
- Hardwired smoke alarm upgrades
- Long-term reliability buyers
Pros
- Drop-in replacement for the discontinued Google Nest Protect, wiring adapter included
- Simple, tool-free hardwired installation with Quick Connect Plug wiring
- Loud built-in siren with voice alerts that identify the type and location of danger
- Photoelectric smoke sensor plus electrochemical CO sensor in one alarm
- Steam-check technology to reduce nuisance kitchen and shower alarms
- Long manufacturer warranty backing the purchase
Cons
- No motion-activated pathway light, unlike the Nest Protect it replaces
- Works only with Google Home; no Alexa, Apple HomeKit, SmartThings, or Matter support
- No automations or self-testing feature
- Some buyers found the app pairing process fussier than Nest's
Who is the First Alert SC5 for?
The SC5 is aimed squarely at homeowners who already have a hardwired smoke alarm circuit, especially those replacing an aging or discontinued Google Nest Protect, since it fits the same ceiling mount and ships with a wiring adapter for that exact swap. It runs on direct household power through a Quick Connect Plug with a lithium battery kept purely as backup during outages, and it links to the Google Home app for mobile alerts. It suits buyers who want dependable, code-compliant smoke and CO protection with light smart-home connectivity, rather than shoppers chasing a broad multi-ecosystem hub, since its integrations begin and end with Google Home.
What buyers love
The recurring theme in owner feedback is how seamless the Nest Protect swap is: the alarm clips onto the existing ceiling mount, and the included wiring harness adapter lets people go from old unit to new in a handful of simple steps with no extra tools. Reviewers also point to the loud built-in siren paired with voice alerts that call out whether the danger is smoke or carbon monoxide, and appreciate being able to silence the unit right from the First Alert or Google Home app. Several owners specifically cite installation ease and Google Home connectivity for remote peace of mind as the standout strengths.
What to know before you buy
The most consistent complaint from former Nest Protect owners is the missing motion-activated pathway light: the SC5 has no built-in light, no pathlight function, and no occupancy or motion sensing, so it will not softly illuminate a dark hallway the way the old Nest unit did. Smart-home reach is also narrower, since the alarm integrates only with Google Home and has no support for Alexa, Apple HomeKit, Samsung SmartThings, IFTTT, or Matter, and there is no automations or self-testing feature. A handful of buyers also found the First Alert app's QR-code pairing fussier than Nest's setup flow, and running Nest and First Alert devices side by side means checking two separate apps.
Is the First Alert SC5 worth it?
Weighed against its role as a direct Nest Protect successor, the SC5 delivers on the fundamentals: hardwired power with lithium battery backup, a photoelectric smoke sensor paired with an electrochemical CO sensor, steam-check logic to cut down on kitchen and shower false alarms, and a lengthy manufacturer warranty that signals confidence in long-term reliability. Buyer sentiment skews positive overall, with the installation experience and Google Home alerts earning consistent praise even as some owners miss the Nest Protect's night light and wish for a more polished companion app. For anyone already in the Google ecosystem who needs a proper hardwired replacement rather than a battery-only alarm, it is a practical, safety-first buy.
Frequently asked questions
Does the First Alert SC5 work as a direct replacement for the Google Nest Protect?
Yes. It is designed to work with and replace the Nest Protect, fitting the same ceiling mount and including a wiring adapter, and it connects through the Google Home app so former Nest Protect owners can stay in a familiar ecosystem.
Does the SC5 run on batteries?
No, it is hardwired to household power through a Quick Connect Plug. A 3V lithium battery is included strictly as backup power to keep the alarm running during outages, not as its main power source.
Does it work with Alexa or Apple HomeKit?
No. The SC5's smart integration is limited to Google Home; it does not support Alexa, Apple HomeKit, Samsung SmartThings, IFTTT, or Matter.
Does the SC5 have a night light like the Nest Protect?
No. It has no built-in light, pathlight, or motion sensor, a change from the Nest Protect that owners switching over tend to notice.
What kind of alerts does the SC5 send?
It sends distinct fire and carbon monoxide alerts with voice announcements naming the type and location of the danger, plus low-battery and end-of-life warnings, all relayed through the First Alert mobile app.
How long is the First Alert SC5 warranty?
It carries a 10-year manufacturer warranty.







