AC Capacitor Replacement: $200 to $400 + Signs It Is Bad

Installed prices include the part and labor. HomeAdvisor's two guides differ; both are shown.

Do this now: AC humming or not starting

Turn the AC off as soon as you hear the outdoor unit hum without starting: HomeGuide says running on a bad capacitor can seriously damage the compressor, a part that costs $1,800 to $2,800 to replace out of warranty.

1. Shut it off first. Turn the system off at the thermostat, then switch off the AC breaker. Open only the panel door to reach the breaker; never remove the panel cover. Leave the outdoor unit's access panels closed: ENERGY STAR notes that faulty electrical connections can cause unsafe operation, and the capacitor inside holds a charge even with the power off (Carrier).
2. Do not touch the capacitor. Carrier says AC capacitors store high-voltage electricity that can cause serious injury or death even when the power is disconnected. OSHA's electrical rule requires workers to discharge capacitors before they work on equipment that has been shut off.
3. Note what you saw and heard: humming, clicking, a fan that does not spin, short on-and-off cycles. Check the thermostat batteries and setting.
4. Keep people cool. If it is over 90 F inside and someone at higher risk is home, move them somewhere cooler; dial 2-1-1 to find air conditioning (CDC).
5. Call with the details: brand, age, and what the unit did before you shut it off.

Is it urgent? When a bad capacitor needs a call today

A failed capacitor is urgent when the house is heating past 90 F with someone at higher risk inside, or when the AC keeps trying to start, because HomeGuide says running it on a bad capacitor can lead to complete system failure. The CDC names people 65 and older, infants and young children, and people with asthma or heart disease as higher risk, and says a fan can raise body temperature above 90 F.

• Humming with no fan: Carrier says a hum from the outdoor unit usually means a motor trying to start. Leave it off.
• The AC shuts off randomly or will not start (HomeGuide). See AC not turning on for the other causes.
• A breaker that trips again after one reset: leave it off; see breaker keeps tripping.

Can it wait? An AC that still cools but short cycles on a mild day can usually wait for a weekday visit. HomeGuide puts after-hours labor at $160 to $250 an hour against $75 to $150 regular, so ask what the visit costs before anyone is sent. Night and weekend steps are on emergency HVAC repair.

Signs of a bad AC capacitor

The most common sign of a bad AC capacitor is an outdoor unit that hums but does not start, which Carrier says usually means a motor trying to start. Other signs from HomeGuide and Carrier:

• The AC stutters or struggles to start, or does not start at all (HomeGuide).
• It shuts off randomly or turns on and off rapidly (short cycling) (HomeGuide, Carrier).
• Warm or lukewarm air from the vents (HomeGuide, Carrier).
• Clicking or humming from the outdoor unit (HomeGuide).
• Higher energy bills, because the motors draw more current (Carrier).
• A swollen top or leaking oil on the capacitor itself (Carrier). Only a technician should open the panel to look.

HomeGuide says a failed start capacitor makes the motor struggle to turn on, while a failed run capacitor can cause overheating, vibration or humming.

Will an AC run with a bad capacitor

An AC may still run on a weak capacitor, with short cycles and lukewarm air, but HomeGuide says running it that way can seriously damage the compressor and fan motor and can cause complete system failure. The math favors stopping early: HomeGuide puts a capacitor at $250 to $400 installed, a fan motor at $200 to $700 and a compressor at $1,800 to $2,800 out of warranty. If the compressor is already failing, see AC compressor repair.

How much does it cost to replace an AC capacitor

Replacing an AC capacitor costs $200 to $400 in HomeAdvisor's June 2026 capacitor guide, and HomeGuide puts the national average at $300, typically $250 to $400. HomeAdvisor says many companies charge an all-inclusive $300 to $600, and its AC repair guide gives a wider $120 to $475. Carrier's figure is $200 to $400 for the part and installation.

Almost all of that is the service visit: the part is $8 to $45 in HomeAdvisor's figures and $15 to $80 in HomeGuide's. HomeAdvisor's part prices by type:

HomeAdvisor says high-end brands add $60 to $140.

A technician may suggest a hard start kit for a compressor that struggles to start; HomeGuide prices one at $100 to $270 installed. Ask for the capacitor's rating and the part price on the invoice.

Can I replace an AC capacitor myself

Carrier strongly recommends that homeowners do not replace an AC capacitor themselves, because capacitors store high-voltage electricity that can cause serious injury or death even with the power disconnected. HomeAdvisor says doing it yourself might save $60 to $200 but is not recommended, citing the risk of electric shock, and that a capacitor's warranty may require professional installation. Testing a capacitor also means opening the unit's electrical compartment, so leave the test to the technician too. Workplace rules treat stored charge the same way: OSHA requires that capacitors be discharged before anyone works on the equipment.

How long does an AC capacitor last

An AC capacitor lasts about 10 years on average in HomeAdvisor's guide, within a 5 to 15 year range, and the other sources run longer:

HomeGuide says power surges and extreme temperatures shorten capacitor life.

A yearly tune-up includes an inspection of the capacitors and contactors in HomeGuide's checklist, which is the cheapest way to catch a weak one before a heat wave; see AC tune-up and maintenance.

Capacitor, contactor or compressor: what else causes the same symptoms

A humming or dead outdoor unit is not always the capacitor. HomeGuide prices the usual suspects: a contactor (the switch that turns the outdoor unit on) at $200 to $450, a fan motor at $200 to $700, and a compressor at $1,800 to $2,800. Warm air with the fan running can also be low refrigerant from a leak; see AC not cooling. Every common fix is priced on AC repair.

What to ask before a capacitor replacement

• Is the service call applied to the repair? HomeGuide says it usually is.
• What is the installed price, and what does the part itself cost?
• Which capacitor failed: start, run or dual run?
• Did you check the compressor and fan motor? A failed capacitor can strain both (HomeGuide).
• Is the part under warranty, and is the system under the manufacturer's warranty?
• License number and proof of insurance.

If the unit is old and the list of problems is growing, compare AC replacement cost. Local guides: AC repair in Phoenix, San Antonio and Orlando. All heating and cooling topics are on the HVAC repair hub, and every trade's prices on home repair costs.

Calls go to an independent company that serves your area and takes this kind of job. Ask for its license number and proof of insurance yourself, and check the license with the state; the HVAC license table lists who issues it in six states. How calls work.