Quick answer
Replacing an AC capacitor costs $150–$350 in the GTA, including the part, the labour and the trip. It is the most common air conditioner repair and takes well under an hour. The part itself is inexpensive; you are paying for the diagnosis, a technician who can test the compressor and fan afterward, and a capacitor rated correctly for your unit. A diagnostic fee of $90–$150 is usually folded in.
An AC capacitor costs $150–$350 to replace, which makes it the cheapest repair that can leave a house without cooling. The capacitor is a small silver can inside the outdoor unit that gives the compressor and fan motor the jolt they need to start and a steady push to keep running. When it weakens, the unit hums, the fan sits still, or the system starts and quits. Here is what you are paying for and how to tell whether it is the real problem.
What is in the price
- The part: most central air conditioners use a dual run capacitor with two ratings on the label, such as 45/5 microfarads at 440 volts. One side serves the compressor, the other the fan. The correct replacement matches both numbers and the voltage rating.
- The labour: pulling power at the disconnect, discharging the old capacitor, swapping it, landing the wires back on the Herm, Fan and Common terminals, then checking the compressor's running amps against its nameplate.
- The diagnostic: confirming the capacitor is the cause and not a symptom. A capacitor that failed because the fan motor is seizing will fail again in a week. The $90–$150 visit fee is credited when we do the repair.
- The trip and the truck stock: carrying the common ratings so the fix happens on the first visit, in the same hour.
How to tell the capacitor has failed
The classic sign is a hum from the outdoor unit with the fan not turning. Look at the top of the can if you can see it through the panel: a bulged or domed lid, or an oily residue around the base, means it has let go. A unit that starts, runs a few seconds and trips is another pattern, covered in why an AC trips the breaker.
A technician tests it with a meter that reads microfarads. Capacitors are rated with a tolerance of about six percent, and one reading more than 10 percent under its label is on its way out even if the unit still starts. That is why a weak capacitor is often caught and replaced at a spring tune-up, before it strands you in July.
Why capacitors fail, and why it happens in a heat wave
Heat is what kills them. A capacitor is rated for a maximum operating temperature, and a condenser sitting on a west-facing wall in Millcroft or Glen Abbey with no shade runs well above ambient on a 32°C afternoon. Age matters too; a capacitor from a 2008 install has done more than 15 summers of that. Voltage swings during summer thunderstorms and the surge when power comes back after an outage finish off the ones that were already weak.
That is why the phone rings for capacitors on the first stretch of 30°C days, the same days everyone else is calling. If your unit is more than 10 years old and has never had the capacitor tested, it is a reasonable thing to ask for at an AC tune-up.
Should you replace it yourself?
The part is easy to buy and the job looks simple on video, which is why we get called to units where it went wrong. A capacitor stores a charge after the power is off and will discharge through a hand. Swapping the Herm and Fan wires puts the wrong capacitance on each motor and can burn out the fan motor. And a homeowner who replaces the capacitor and finds the unit still humming has spent the money and still needs the visit. It is a fast, inexpensive call; let a technician do it with the power verified off at the disconnect.
Warranty covers the part, not the labour, and repeat failures point elsewhere
If the air conditioner is under 10 years old and was registered at installation, the capacitor is usually covered as a part under the manufacturer's parts warranty. Labour is not, which is why the bill still lands close to $150–$350 either way. Our guide to HVAC warranty coverage explains what registration changes.
A capacitor that fails twice in two summers is pointing at something else: a fan motor drawing too many amps, a compressor that is getting hard to start, or low voltage at the unit. On an ageing compressor a hard-start kit, which adds a separate start capacitor and relay, can buy time. If the compressor itself is the issue, the numbers are different; see what an AC compressor costs to replace.
ZK Mechanical stocks the common capacitor ratings on the truck for Burlington AC repair and the surrounding area, with written pricing before the panel comes off. If your unit is humming and not starting, switch it off at the thermostat and book a repair; a failed capacitor left to hum overheats the compressor.