What is the cost to install smoke and carbon monoxide detectors to meet Ontario code?

Installing a code-compliant hardwired, interconnected smoke and carbon monoxide detection system in a GTA home typically costs between $800 and $2,500, depending on the size of your home and how many devices are needed. Ontario Fire Code requires hardwired smoke alarms on every level of the home and outside each sleeping area, plus CO alarms near all sleeping areas in homes with fuel-burning appliances, attached garages, or fireplaces.

A typical three-bedroom, two-storey GTA home needs approximately four to six smoke alarms and two to three CO alarms to meet code. Combination smoke/CO units, which serve both functions in a single device, are increasingly popular and can reduce the total number of devices needed. Individual hardwired smoke alarms cost $30 to $60 per device, while combination smoke/CO units run $50 to $100 each. The devices themselves represent a relatively small portion of the total cost — it is the wiring and installation labour that makes up the bulk of the expense.

"Interconnected" means that when one alarm activates, all alarms in the home sound simultaneously. This requires either a dedicated low-voltage interconnect wire running between all devices, or wireless interconnection capability built into the alarms. Hardwired interconnected systems use a three-conductor cable (NMD90 14/3) running from device to device in a daisy-chain configuration, with the interconnect wire carrying the signal between units. Running this cable through finished walls and ceilings is where the labour cost accumulates. In a home with accessible attic space above the upper floor, the electrician can route much of the wiring through the attic, keeping the cost at the lower end of the range. In a two-storey home with no attic access — or a home where the smoke alarm locations require running cable through finished walls between floors — the electrician may need to fish wire through wall cavities, cut access holes, and patch afterward, pushing costs higher.

For a new construction or gut renovation where walls are open, the wiring cost drops substantially because the electrician can run cable freely before drywall goes up. In this scenario, the smoke and CO alarm wiring is typically included in the overall electrical rough-in, and the per-device installed cost might be as low as $80 to $150. In a finished home requiring retrofit installation, per-device installed costs run $150 to $300.

Ontario has specific requirements that affect the installation. Smoke alarms must be installed on the ceiling or within 30 centimetres of the ceiling on a wall. They cannot be installed near kitchen areas, bathrooms, or forced-air ducts where false alarms are common — the electrician positions them according to manufacturer specifications and code requirements. CO alarms must be installed near sleeping areas and are typically placed in hallways outside bedrooms. All devices must be CSA-approved.

The ESA permit is required for new hardwired alarm circuits, typically $100 to $200 for this scope of work. The inspector will verify proper placement, interconnection functionality (testing that triggering one alarm sounds all of them), and correct wiring. This documentation is important — at resale, home inspectors check for code-compliant smoke and CO detection, and the ESA certificate proves the system was professionally installed and inspected.

One important note for older GTA homes: if your home currently has battery-only smoke detectors, upgrading to hardwired interconnected units is required by code whenever you undertake a renovation that requires a building permit. Even without a renovation trigger, upgrading to hardwired interconnected detection is one of the most important life-safety improvements you can make. Get matched with a licensed electrician for a free estimate through Toronto Electrical Repair and the Toronto Construction Network.