Not available on Amazon UK
Updated October 2026
Data from Amazon and official First Alert and Google sites.
2026 verdict
The Google Nest Protect (Wired) is the more capable hardwired smoke and CO alarm of these two, and the better reviewed.
It adds occupancy, temperature, humidity, ambient-light and motion sensing, an automatic pathlight, a monthly self-test and Home Assistant support, none of which the First Alert SC5 Hardwire Smart Smoke & CO Alarm carries. Both detect smoke and carbon monoxide, interconnect so all units sound together, run on mains power with battery backup and voice an early warning, and both are managed through Google Home rather than Alexa, Apple HomeKit or Matter. The First Alert SC5 Hardwire Smart Smoke & CO Alarm answers with a lower price and a longer 10-year warranty against 2 years. Pick the Google Nest Protect (Wired) for the richer sensing and smart features, and the First Alert SC5 Hardwire Smart Smoke & CO Alarm for value.
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| Feature | First Alert SC5 Hardwire Smart Smoke & CO Alarm | Google Nest Protect (Wired) | Winner |
|---|---|---|---|
| Rating | 3.2 | 4.6 | Google Nest Protect (Wired) |
| 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 (Wired) |
| Sensors | Smoke, CO | Smoke, CO, Occupancy, Temperature, Humidity, Ambient Light, Motion | Google Nest Protect (Wired) |
| Built-in Light | NO | YES | Google Nest Protect (Wired) |
| Tests Itself | NO | YES | Google Nest Protect (Wired) |
| Pathlight | NO | YES | Google Nest Protect (Wired) |
| 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
Sensors
The Google Nest Protect (Wired) adds occupancy, temperature, humidity, ambient-light and motion sensing on top of smoke and CO. The First Alert SC5 Hardwire Smart Smoke & CO Alarm senses smoke and carbon monoxide only.
Pathlight and light
Only the Google Nest Protect (Wired) has a night pathlight and a built-in light. The First Alert SC5 Hardwire Smart Smoke & CO Alarm has neither, a gap owners switching from Nest notice immediately.
Self-test
The Google Nest Protect (Wired) tests its sensors over 400 times a day and emails a monthly report. The First Alert SC5 Hardwire Smart Smoke & CO Alarm has no self-test.
Warranty
Ten years on the First Alert SC5 Hardwire Smart Smoke & CO Alarm against two on the Google Nest Protect (Wired).
Price and availability
The First Alert SC5 Hardwire Smart Smoke & CO Alarm is the lower priced and currently available option. Google has discontinued the Nest Protect, so the wired model is limited to remaining retail stock.
Home Assistant
The Google Nest Protect (Wired) works in Home Assistant through a community integration, giving it one more smart home path than the First Alert SC5 Hardwire Smart Smoke & CO Alarm.
Which one to buy if
- you want the richest sensing and a night pathlight
Only the Google Nest Protect (Wired) adds occupancy, temperature, humidity, light, motion and a pathlight.
- you are replacing a failed or discontinued Nest Protect and want current stock
The First Alert SC5 Hardwire Smart Smoke & CO Alarm is still in production and drops into the same mount.
- you want the longest warranty
Ten years on the First Alert SC5 Hardwire Smart Smoke & CO Alarm against two on the Google Nest Protect (Wired).
- you want self-testing with a monthly report
The Google Nest Protect (Wired) checks itself continuously and emails the result; the First Alert does not.
- you are on a tighter budget
The First Alert SC5 Hardwire Smart Smoke & CO Alarm costs less.
Not available on Amazon UK
- + Warranty: 10 years
- - Rating: 3.2 vs 4.6
- - Connectivity: 2.4 GHz WiFi vs 2.4 GHz WiFi, Bluetooth, Other
Winner
$499.99
- + Rating: 4.6
- + 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 that hardwiring ends the routine battery change, installation is quick, and the spoken early warning that names the room is the feature they value most. Google Nest Protect (Wired) owners single out the self-testing with a monthly report, the pathlight, the wireless interconnection that works even with Wi-Fi off and the way it can tell a Nest thermostat to cut heat on CO; their complaints are the high price, that it only interconnects with other Nest Protects, and that it lives in the Nest app with no Alexa, HomeKit or Matter. First Alert SC5 Hardwire Smart Smoke & CO Alarm owners praise how seamlessly it replaces a Nest Protect, but miss the pathlight and find the First Alert app less polished, with a handful meeting QR pairing friction.
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 (Wired)
Loading price history...
Frequently Asked Questions
Which is better overall: First Alert SC5 Hardwire Smart Smoke & CO Alarm or Google Nest Protect (Wired)?
The Google Nest Protect (Wired) 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 fresh, currently available replacement.
What is the biggest difference between the First Alert SC5 Hardwire Smart Smoke & CO Alarm and the Google Nest Protect (Wired)?
Sensing and extras. The Google Nest Protect (Wired) adds occupancy, temperature, humidity, ambient-light and motion sensing plus a pathlight and monthly self-test, while the First Alert SC5 Hardwire Smart Smoke & CO Alarm senses smoke and CO only.
Do the First Alert SC5 Hardwire Smart Smoke & CO Alarm and the Google Nest Protect (Wired) work with Alexa or Apple HomeKit?
No, neither does. Both are managed through Google Home, and the Google Nest Protect (Wired) also works with Home Assistant. Neither supports Alexa, Apple HomeKit, SmartThings or Matter.
Does the First Alert SC5 replace a Google Nest Protect?
Yes. The First Alert SC5 Hardwire Smart Smoke & CO Alarm fits the same ceiling mount and includes a wiring adapter, so it is a drop-in swap for the discontinued Google Nest Protect (Wired).
Which has a longer warranty?
The First Alert SC5 Hardwire Smart Smoke & CO Alarm, at 10 years against 2 years on the Google Nest Protect (Wired).
Who should buy the Google Nest Protect (Wired)?
Buyers with existing alarm wiring who want the extra sensors, pathlight and self-testing, are comfortable with Google Home and Home Assistant, and can find remaining retail stock.
Full comparison table
Compare all 25 Smoke & CO Detectors side by side
You are looking at two of them. The full table lines up all Smoke & CO Detectors in the catalog with the same specs, so you can filter by what you need and sort by price or rating.
- 25 Smoke & CO Detectors
- 44 specs compared
- 41 filters
YoLinkPhotoelectric Smoke Alarm
HeimanMatter Smoke Detector S1-TM
$49.98- Google
Nest Protect (Wired)
$499.99 
X-SenseWi-Fi CO Alarm
€39.99
X-SenseSC07-MR Smart Smoke & CO Alarm
HeimanHS1SA-E Zigbee Smoke Alarm
€34.99
X-SenseWiFi Smoke & CO Detector
€59.18
X-SenseWi-Fi Smoke Alarm
€24.06
GoogleNest Protect (Battery)
ShellySmoke Alarm
12% OFF€59.99€52.54
EufySmoke Alarm E10
17% OFF$59.99$49.99
X-SenseXC0M-iR Smart Carbon Monoxide Alarm with Voice Alerts
15% OFF
€35.99€30.59
HeimanInterconnected Smoke Alarm S1-R
$25.99
AqaraSmart Smoke Detector
11% OFF€44.99€39.99
KiddeSmart Smoke & CO Detector with Ring
$69.97
HeimanInterconnected CO Alarm C1-R
10% OFF$29.98$26.99
First AlertSC5 Battery Smart Smoke & CO Alarm
HeimanSmart CO Alarm
17% OFF$59.99$49.99
HeimanMatter Smoke Detector S1-M
$39.99
First AlertSMCO410 Smoke Detector & CO Alarm
$64.98
- Smoke & CO DetectorsFirst Alert
SC5 Battery Smart Smoke & CO Alarm
3.8(81) - Smoke & CO DetectorsFirst Alert
SC5 Hardwire Smart Smoke & CO Alarm
3.2(124) - Smoke & CO DetectorsFirst Alert
SMCO410 Smoke Detector & CO Alarm
3.5(268)$64.98 
Water Shutoff ValvesFirst AlertL5 WiFi Water Leak Shutoff Valve
4.2(3)$284.60
CamerasGoogleNest Cam (outdoor or indoor, battery)
4.1(6,079)10% OFF$199.99$179.99
CamerasGoogleNest Cam Floodlight
4.4(1,906)8% OFF$279.99$257.99
CamerasGoogleNest Cam Indoor (Wired, 3rd Gen)
4.5(1,097)$129.00
CamerasGoogleNest Cam Outdoor (Wired, 2nd Gen)
4.4(790)25% OFF$199.99$149.99
CamerasGoogleNest Cam (indoor, wired)
4.4(5,424)$130.63
DisplaysGoogleNest Hub (2nd Gen)
4.2(1,152)$299.99
DisplaysGoogleNest Hub Max
4.3(215)
DoorbellsGoogleNest Doorbell (battery)
4.2(5,092)10% OFF$199.99$179.99
DoorbellsGoogleNest Doorbell (wired, 3rd Gen)
4.4(1,093)5% OFF$199.99$190.30
DoorbellsGoogleNest Doorbell (wired, 2nd Gen)
4.4(1,130)$129.99
Door LocksGoogleNest x Yale Lock
4.2(2,028)$229.99
RoutersGoogleNest WiFi Pro
4.0(2,494)- Smoke & CO DetectorsGoogle
Nest Protect (Battery)
4.4(7,508) - Smoke & CO DetectorsGoogle
Nest Protect (Wired)
4.6(4,630)$499.99 
SpeakersGoogleNest Audio
4.4(222)
SpeakersGoogleNest Mini (2nd gen)
4.3(2,150)
Temperature & Humidity SensorsGoogleNest Temperature Sensor (2nd gen)
4.4(1,328)$39.98
Temperature & Humidity SensorsGoogleNest Temperature Sensor
4.6(16,633)$39.00
ThermostatsGoogleNest Learning Thermostat (4th gen)
4.4(2,602)14% OFF$279.99$239.99
ThermostatsGoogleNest Learning Thermostat
4.2(358)