Winner
Updated November 2026
Data from the official First Alert and Shelly sites.
2026 verdict
The First Alert SC5 Battery Smart Smoke & CO Alarm wins this smoke alarm comparison on the strength of its combined smoke and carbon monoxide sensing, its broader alert set and its 10-year warranty and battery life.
It adds a CO sensor, CO and low-battery alerts, steam-check nuisance filtering and voice alerts naming the type and location of danger, all things the smoke-only Shelly Plus Smoke Alarm lacks, and its decade-long warranty and battery outlast the Shelly's 5-year battery rating. The Shelly Plus Smoke Alarm is far from outmatched, though: it is the more affordable and better-rated unit, pairs hub-free over Wi-Fi, integrates with Google Home, SmartThings and Home Assistant and adds a built-in light, making it the pick for automation-focused homes that do not need CO coverage. Buy the First Alert SC5 for combined smoke and CO safety with a long warranty; buy the Shelly Plus for a cheaper, well-rated, integration-rich smoke alarm.
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The biggest differences
Where these two are furthest apart, and by how much.
- Warranty3.3×First Alert SC5 Battery Smart Smoke & CO Alarm10 years vs 3 years
- Battery Life2×First Alert SC5 Battery Smart Smoke & CO Alarm10 years vs 5 years
| Feature | First Alert SC5 Battery Smart Smoke & CO Alarm | Shelly Plus Smoke Alarm | Winner |
|---|---|---|---|
| Rating | 3.6 | 4.4 | Shelly Plus Smoke Alarm |
| Warranty | 10 years | 3 years | First Alert SC5 Battery Smart Smoke & CO Alarm |
| Battery Life | 10 years | 5 years | First Alert SC5 Battery Smart Smoke & CO Alarm |
| Connectivity | 2.4 GHz WiFi | 2.4 GHz WiFi, Bluetooth | Shelly Plus Smoke Alarm |
| Integrations | Google Home | Google Home, Samsung SmartThings, Home Assistant | Shelly Plus Smoke Alarm |
| Sensors | Smoke, CO | Smoke | First Alert SC5 Battery Smart Smoke & CO Alarm |
| Alerts | Fire Alerts, CO Alerts, Low Battery Alerts | Fire Alerts, Low Battery Alerts | First Alert SC5 Battery Smart Smoke & CO Alarm |
| Built-in Light | NO | YES | Shelly Plus Smoke Alarm |
| Steam Check | YES | NO | First Alert SC5 Battery Smart Smoke & CO Alarm |
| Screen | NO | NO | Tie |
| Built-in Siren | YES | YES | Tie |
| Tests Itself | NO | NO | Tie |
Winner
- + Warranty: 10 years
- + Battery Life: 10 years
- + Sensors: Smoke, CO
- - Rating: 3.6 vs 4.4
- - Connectivity: 2.4 GHz WiFi vs 2.4 GHz WiFi, Bluetooth
7% OFF
£64.81
£69.74
- + Rating: 4.4
- + Connectivity: 2.4 GHz WiFi, Bluetooth
- + Integrations: Google Home, Samsung SmartThings, Home Assistant
- - Warranty: 3 years vs 10 years
- - Battery Life: 5 years vs 10 years
Frequently Asked Questions
Which is better overall: First Alert SC5 Battery Smart Smoke & CO Alarm or Shelly Plus Smoke Alarm?
The First Alert SC5 Battery Smart Smoke & CO Alarm is better overall as a safety device because it adds carbon monoxide detection, more alerts and a 10-year warranty. The Shelly Plus Smoke Alarm counters as the more affordable, better-rated unit with hub-free Wi-Fi and wider integrations, but it detects smoke only.
What is the biggest difference between the First Alert SC5 Battery Smart Smoke & CO Alarm and the Shelly Plus Smoke Alarm?
The biggest difference is that the First Alert SC5 Battery Smart Smoke & CO Alarm detects both smoke and carbon monoxide, while the Shelly Plus Smoke Alarm detects smoke only. The Shelly makes up ground with a lower price, higher rating and integration with Google Home, SmartThings and Home Assistant.
Does the Shelly Plus Smoke Alarm detect carbon monoxide?
No. The Shelly Plus Smoke Alarm is a smoke-only device with fire and low-battery alerts and no CO sensor. The First Alert SC5 Battery Smart Smoke & CO Alarm adds an electrochemical carbon monoxide sensor plus CO alerts, covering both hazards from one unit.
Which alarm integrates with more smart-home platforms?
The Shelly Plus Smoke Alarm integrates with more platforms, working with Google Home, Samsung SmartThings and Home Assistant over hub-free Wi-Fi. The First Alert SC5 Battery Smart Smoke & CO Alarm works with Google Home and focuses on standalone smoke and CO protection.
Who should buy the First Alert SC5 Battery Smart Smoke & CO Alarm?
Buy the First Alert SC5 Battery Smart Smoke & CO Alarm if you want combined smoke and carbon monoxide detection with steam-check, CO and low-battery alerts, voice alerts naming the danger, and a long 10-year warranty and battery life.
Who should buy the Shelly Plus Smoke Alarm?
Buy the Shelly Plus Smoke Alarm if you want the more affordable, better-rated option with hub-free Wi-Fi setup and integration with Google Home, SmartThings and Home Assistant, and you do not need carbon monoxide detection.
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