In my last review, I tested battery-powered carbon monoxide detectors, highlighting their portability and independence from power outlets. But what if you prefer a plug-in model that doesn’t rely on batteries for daily operation?
That’s where this comparison comes in. I tested some of the most popular plug-in CO detectors to see how they compare in terms of reliability, usability, and features.
If you’re looking for a CO alarm that plugs directly into an outlet, this guide will help you choose the best one.
Plug-In CO Detectors: Reliable and Convenient
Plug-in CO detectors are a breeze to install—just plug them into any standard outlet, and you’re good to go. Many models come with battery backups, ensuring continuous monitoring even during power outages.
| Model | Dimensions (D x W x H) | Weight (oz) | Display | Sensor Type | Backup Battery | Price Range |
| Kidde KN-COB-DP2 | 2.75″ x 4.5″ x 1.5″ | 8.0 | No | Electrochemical | No | $23-$28 |
| Kidde KN-COPP-3 | 2.75″ x 4.5″ x 1.5″ | 8.0 | Yes | Electrochemical | Yes | $40-$45 |
| First Alert CO600 | 3.4″ x 1.38″ x 5″ | 6.4 | No | Electrochemical | No | $23-$28 |
| First Alert CO605 | 3.4″ x 1.38″ x 5″ | 6.4 | No | Electrochemical | Yes | $25-$30 |
| First Alert CO615 | 3.4″ x 1.9″ x 5″ | 13.6 | Yes | Electrochemical | Yes | $30-$35 |
My Experience with Each Model
Kidde KN-COB-DP2
The Kidde KN-COB-DP2 is a simple plug-and-play CO detector with no digital display or backup battery.
While testing it, I appreciated how compact and unobtrusive it was—it doesn’t stick out too much in a room.
However, because it lacks a display, you won’t get real-time CO level readings, which some users might find inconvenient. A few buyers have noted that it can be a bit difficult to test manually, as it lacks a peak level memory. That said, it’s an affordable and effective choice if you’re looking for a basic plug-in CO alarm.
Kidde KN-COPP-3
The Kidde KN-COPP-3 immediately stood out because of its digital display, which provides real-time CO readings.
I found this particularly useful during testing, as it allowed me to see how even minor environmental changes affected CO levels.
Another great feature is its peak level memory, which stores the highest CO level recorded, making it easier to track possible exposure over time. Some users mentioned that the display is a little small, but I didn’t find it difficult to read. Given its 10-year lifespan and battery backup, this model strikes a great balance between affordability and functionality.
First Alert CO600
The First Alert CO600 is another display-free model that keeps things minimalistic.
It’s lightweight and easy to install, taking only a few seconds to set up. However, I noticed that since it doesn’t have a battery backup, it becomes useless in a power outage, which might be a deal-breaker for some.
I also found that the alarm was loud enough to hear from another room, but some users mentioned that it can be overly sensitive, occasionally going off due to environmental factors. If you want a no-frills detector, this one does the job, but the lack of backup power is something to keep in mind.
First Alert CO605
The First Alert CO605 is essentially an upgraded version of the CO600, with one key improvement—a 9V backup battery. This means it keeps monitoring CO levels even if your power goes out, which is a big plus for reliability.
I found that installation was effortless, and I liked that it had a test/reset button that was easy to use.
Some users noted that the battery compartment could be slightly tricky to open, but overall, this detector feels like a more practical option compared to battery-free models.
First Alert CO615
The First Alert CO615 is another digital display model, and it comes with a backlit screen, making it easier to read than the Kidde KN-COPP-3.
One thing I noticed while testing was how convenient the silence button was—if you get a false alarm, you don’t have to struggle to reset it. The alarm itself is loud and distinct, ensuring you won’t miss it.
Some buyers pointed out that the CO615’s backup batteries drain faster than expected, so replacing them regularly is important. Still, with its clear display and reliable performance, this model is a strong contender if you want a digital plug-in CO detector.
Final Thoughts
When selecting a plug-in CO detector, consider whether you need a digital display and battery backup. If you just need a basic, affordable option, the First Alert CO600 or Kidde KN-COB-DP2 are decent choices, though they lack a backup battery.
If continuous monitoring and real-time CO level displays are priorities, the Kidde KN-COPP-3 or First Alert CO615 are excellent options. The First Alert CO605 strikes a balance between affordability and practicality with its backup battery.
No matter which one you choose, make sure to place CO detectors near sleeping areas and on every level of your home for maximum safety.
Stay safe out there!