How much does smoke detector installation cost?

Straight detector replacement is usually priced per device

For a typical replacement, smoke detector installation cost is usually based on the number of expired or missing units. In the GTA, replacing existing alarms with combination smoke/CO units with battery backup usually lands at $90–$150 per unit installed.

That price assumes there is already a suitable alarm location and the existing wiring or mounting location can be reused. It covers removing the old device, installing the new alarm, confirming power and battery backup, and testing the alarm at the button. If the old alarm is hardwired, we also check the interconnect conductor so one alarm triggers the rest of the system.

The price changes when we have to add wiring, move an alarm, fish cable through finished ceilings, or correct an older setup where alarms were never interconnected. In those cases, the work is quoted in writing after a site visit because access matters. A bungalow with an open basement ceiling is very different from a finished three-storey home with plaster ceilings.

Common cost factors include:

• Number of alarms: every storey, sleeping area, and renovation zone may affect the count.
• Device type: smoke-only, CO-only, or combination smoke/CO alarms.
• Power source: battery-only replacement versus hardwired 120V with battery backup.
• Interconnection: whether alarms already communicate or need new interconnect wiring.
• Ceiling access: attic access, open joists, finished drywall, plaster, or concrete condo ceilings.
• Permit scope: new wiring normally needs ESA notification and inspection.

For most homeowners, the first step is not choosing the cheapest device. It is confirming how many alarms the home should have, where they should be, and whether the existing units are expired. City Power Electrical Services is a Licensed Electrical Contractor, ECRA/ESA #7015314, and we provide free written estimates for smoke and CO detector work in Toronto and the GTA.

For service details, see our smoke and CO detector installation page, or compare the deeper cost breakdown in our hardwired smoke detector cost guide for Ontario.

Hardwired, interconnected alarms cost more when new wiring is needed

Hardwired smoke detector installation costs more than simple replacement because the electrician is installing a life-safety circuit path, not just swapping a device. The alarm needs permanent 120V power, battery backup, and in many setups an interconnect conductor so all alarms sound together.

A hardwired interconnected alarm typically has:

In many Ontario renovation scenarios, hardwired interconnected smoke alarms become part of the permit conversation. Finished basements, additions, major interior renovations, and legal second-suite work often trigger updated alarm requirements. The exact requirement depends on the building permit scope, the existing house, and the authority reviewing the project, but the direction is consistent: sleeping areas need reliable warning, and alarms often need to sound together.

Where new wiring is installed, an ESA notification is normally filed by the licensed electrical contractor. ESA inspection may check that the wiring method is suitable, boxes are accessible, connections are enclosed, and the alarms are installed as part of a compliant electrical system. The building inspector or municipal plan examiner may separately care about alarm locations and whether the finished renovation meets the Ontario Building Code and Ontario Fire Code expectations.

Hardwired upgrades are most often quoted after a site visit because we need to see:

• Whether the panel has a suitable circuit available.
• Whether the alarms can be supplied from an existing lighting circuit or need another route.
• Whether finished ceilings require drywall openings.
• Whether the attic, basement, or mechanical room gives a practical path.
• Whether the home already has a three-wire interconnect cable between alarm locations.
• Whether the renovation includes bedrooms, a basement suite, or a fuel-burning appliance area.

If you are renovating a basement, it is usually cheaper and cleaner to plan detector wiring at the same time as other electrical rough-in. The same visit may include lighting, receptacles, bathroom fan wiring, and detector rough-in, instead of cutting finished ceilings later. If your project includes a washroom fan, the related cost question is covered here: how much does bathroom fan installation cost?.

The right locations matter as much as the device price

The correct smoke detector installation cost depends on the number of required locations, not just the number of old alarms you currently have. Many homes are under-protected because they still follow an old layout: one alarm in the hallway and nothing on the lower level, upper level, or inside sleeping rooms.

For Ontario homes, the exact rules can depend on the age of the home and the work being done, but a practical inspection starts with these locations:

• Each storey: including the basement.
• Outside sleeping areas: usually in the hall serving bedrooms.
• Bedrooms in newer or substantially renovated areas: often required under current construction standards.
• Adjacent to sleeping areas for CO protection: especially where there is an attached garage or fuel-burning appliance.
• Basement suite or second unit areas: interconnected smoke/CO coverage is a major part of making the electrical and life-safety system acceptable.

Placement details also matter. Smoke alarms should not be installed where cooking steam, shower humidity, supply-air drafts, or dead-air corners cause nuisance alarms or delayed detection. CO alarms are often placed near sleeping areas because carbon monoxide protection is about waking occupants before exposure becomes dangerous. Combination devices can simplify the layout, but only if the device is approved for the location and the placement works for both smoke and CO detection.

We also look at device expiry dates. Many smoke alarms and CO alarms are not meant to stay in service indefinitely. The replacement date is usually printed on the back or side of the unit. A detector can still beep when tested and still be past its listed service life. If the date is unreadable, the unit is yellowed, or the home has a mix of unknown devices, replacement is usually the safer path.

A good detector layout avoids three common problems:

• Too few devices: one alarm cannot protect every bedroom level and basement area.
• Wrong device type: a smoke-only alarm does not provide CO protection.
• No interconnection: a basement alarm may not wake someone sleeping upstairs.

This is why the cheapest quote is not always the safest quote. The electrician should tell you what is being installed, where it goes, whether it is interconnected, whether battery backup is included, and whether ESA notification applies.

New wiring, renovations, and second suites should be quoted after inspection

If your project involves new detector wiring, treat it as part of the electrical permit and renovation plan. A simple device swap can be priced per unit, but adding new hardwired interconnected smoke/CO alarms is a site-specific job.

This is especially important in finished basements and second-suite projects. Detector wiring may need to coordinate with:

• Dedicated kitchen or laundry circuits.
• Bedroom and living-area lighting circuits.
• Bathroom fan and lighting controls.
• Fire separation work in ceilings.
• Panel capacity and circuit labelling.
• Access panels, bulkheads, or finished drywall repairs.

Where a renovation requires hardwired alarms, we prefer to rough in the wiring before drywall. That allows proper box placement, a clean interconnect path, and inspection before the ceiling is closed. After drywall, fishing cable may still be possible, but it can take longer and may require small access openings.

ESA inspection for new detector wiring is not the same as a home inspector’s visual comment. ESA is looking at the electrical installation: wiring method, junction boxes, grounding and bonding where applicable, circuit protection, and whether the work matches the filed notification. The municipal building department may also require alarm compliance before closing a building permit.

If you are comparing detector work with other small electrical jobs, remember that alarms are life-safety devices. A light fixture that fails is inconvenient. A non-interconnected alarm in the wrong location can mean the person farthest from the fire hears it too late. For ordinary fixture pricing, see how much does light fixture installation cost?, but do not use fixture pricing as a substitute for detector wiring.

You can keep costs down by replacing expired alarms together

The cleanest way to control smoke detector installation cost is to replace all expired or mismatched alarms in one visit. It reduces repeat troubleshooting, keeps the devices on the same replacement cycle, and lets the electrician test the whole alarm network at once.

Before calling, take a quick inventory:

• Count the alarms on each storey.
• Note which ones are smoke-only, CO-only, or combination units.
• Check the expiry or manufacture date on each device.
• Confirm whether pressing one alarm’s test button triggers the others.
• Note any rooms where alarms are missing after a renovation.
• Tell us whether the home has an attached garage, gas furnace, gas water heater, fireplace, or other fuel-burning equipment.

Do not assume a detector is acceptable just because it has a green light. The green light may only show that the unit has power. It does not prove the sensor is within its service life, that the interconnect works, or that the device is in the right location. If your question is about an indicator light rather than installation price, see why your smoke detector is flashing red.

For straight replacements, the per-device price gives you a useful budget. For hardwired additions, basement renovations, second suites, or homes with no existing interconnect, expect a written quote after the site visit. The quote should clearly separate device replacement from new wiring, ESA notification where required, patching assumptions, and any related electrical corrections found during the work.

A safe detector job is simple to describe: the right alarms, in the right places, powered properly, interconnected where required, backed up by batteries, and installed under the correct inspection process when new wiring is involved.