A CO detector should be in every home, regardless of whether it is all electric or not.
If the home has a garage or carport, or if you leave a car or tractor running close to the house, carbon monoxide can seep in. If you use a generator during a power outage, carbon monoxide can seep in. Also, a fireplace is dangerous if the chimney/flue is not venting properly.
At a cost of only $40 - $50 each, a carbon monoxide detector should be in every home, either in the bedrooms or in the hallway just outside the bedrooms. In my opinion, it is cheap insurance.
Bob