The answer to 'how much to replace carbon monoxide detector' is that the cost can vary significantly depending on several factors. As a general range, you can expect to pay anywhere from $20 to $100 or more to replace a carbon monoxide detector in your home.
The specific cost will depend on the type of detector (basic vs. smart/connected), the brand and features, whether it needs to be hardwired or is battery-powered, and the labor costs in your local area. Additionally, if you need to replace multiple detectors throughout your home, the total cost will be higher.