Smoke and CO Detector Installation Cost Calculator

Battery-only detectors cost $20-$50 each and can be self-installed anywhere. Hardwired interconnected detectors ($30-$100 each) require an electrician to wire them to 120V power and interconnect them so all alarms sound when one activates. The interconnection is what building codes increasingly require and what saves lives - when the basement detector goes off, you hear it upstairs.

Minimum code typically requires one per floor, one outside each sleeping area, and one in each bedroom. A 3-bedroom 2-story home needs at minimum 7-8 detectors to meet current NFPA 72 recommendations. The per-unit cost drops when an electrician is already on-site for the service call.

Homes built after the mid-1990s typically have pre-wired interconnect wire (three-wire with red interconnect) at each detector location. Connecting new detectors to these boxes is straightforward. Older homes without this wiring require either new wire runs or a wireless interconnect system ($30-$60 extra per unit) where all detectors communicate via radio signal without additional wiring.

Combination smoke and carbon monoxide detectors are $10-$20 more per unit than smoke-only. CO detectors are required near sleeping areas in most states with attached garages or fossil fuel appliances (furnaces, water heaters, gas ranges). Installing combination units is nearly always worth the small cost premium.

Standard hardwired detector: $30-$50. Smart detector (Nest Protect, Kidde Voice Wi-Fi): $100-$150 each. Smart detectors send phone alerts when you're away, identify the source room, provide hush controls from your phone, and run monthly self-tests. A 10-unit smart system costs $400-$600 more in hardware but provides truly useful remote monitoring.