AC Capacitor Replacement Cost

Understanding AC Capacitor Replacement

AC capacitors are small cylindrical components that store and release electrical energy to start and run your air conditioner's motors. Despite their small size and low cost, capacitors are among the most common AC repair needs—and one of the most dangerous to work on due to stored electrical charges.

Understanding AC capacitor replacement cost helps you evaluate service quotes and decide whether DIY replacement is appropriate for your skill level. The repair itself costs $110-$300 with professional installation, while the part alone runs just $10-$50.

Types of AC Capacitors and Costs

Start Capacitors

Parts Cost: $10-$25 Installed Cost: $110-$225

Function: Start capacitors provide a surge of power to help motors overcome inertia and begin spinning. They connect briefly during startup (typically less than 1 second) and then disconnect.

Characteristics:

• Higher capacitance: 70-120 μF typical
• Connected via start relay or potential relay
• Black plastic case common
• Round shape, two terminals
• Only energized during startup

Common Applications:

• Compressor hard-start assistance
• High-efficiency units
• Older AC systems

Run Capacitors

Parts Cost: $10-$30 Installed Cost: $110-$230

Function: Run capacitors provide continuous power to motors during operation, improving efficiency and maintaining proper phase angle for motor operation.

Characteristics:

• Lower capacitance: 5-80 μF typical
• Stays connected during operation
• Oval or round metal case
• Oil-filled for heat dissipation
• Voltage ratings: 370V or 440V typical

Common Applications:

• Condenser fan motor
• Compressor motor (single-capacity systems)
• Indoor blower motor

Dual Run Capacitors

Parts Cost: $15-$50 Installed Cost: $115-$300

Function: Dual run capacitors combine two capacitors in one housing—typically one section for the compressor and one for the condenser fan motor.

Characteristics:

• Three terminals: Common (C), Herm (compressor), Fan
• Most common in modern residential AC
• Oval metal case
• Rated in format: 35+5 μF (35 for compressor, 5 for fan)
• More convenient but single point of failure

Common Ratings:

Hard Start Kits

Parts Cost: $30-$80 Installed Cost: $130-$280

Function: Hard start kits combine a start capacitor with a relay to help compressors start under difficult conditions (high ambient temperature, low voltage, short cycling).

Benefits:

• Reduces compressor startup stress
• Helps older compressors start reliably
• Extends compressor life
• Reduces electrical demand during startup

Best for:

• Aging AC systems
• Compressors showing hard-start symptoms
• Areas with voltage fluctuations
• Systems that short cycle

How to Test AC Capacitors

Visual Inspection

Before testing electrically, inspect the capacitor visually:

Signs of Failure:

• Bulging or swollen top
• Rust or corrosion on case
• Oil leaking from bottom
• Burn marks or discoloration
• Melted plastic terminals

Any of these signs indicates the capacitor should be replaced—no further testing needed.

Multimeter Testing

Required Equipment:

• Digital multimeter with capacitance (μF) function
• Insulated screwdriver for discharge
• Insulated gloves and safety glasses

Testing Procedure:

1. Turn off all power

   • Shut off at disconnect box
   • Turn off at circuit breaker
   • Wait 5 minutes

2. Discharge the capacitor

   • Using insulated screwdriver, bridge terminals
   • For dual capacitors: C to Fan, then C to Herm
   • Listen/look for spark (may be minimal if already discharged)

3. Disconnect wires

   • Take photo first to document connections
   • Remove wires from terminals
   • Note: some capacitors have push-on connectors, others have screws

4. Set multimeter to capacitance

   • Select μF or capacitance mode
   • Range should cover expected capacitor rating

5. Test capacitance

   • Touch probes to terminals
   • For dual: test C to Fan and C to Herm separately
   • Compare reading to rated value on label

Interpreting Results:

DIY Capacitor Replacement Guide

CRITICAL SAFETY WARNING

CAPACITORS STORE LETHAL ELECTRICAL CHARGES EVEN WHEN POWER IS OFF.

Before touching any capacitor terminals:

1. Turn off power at disconnect AND breaker
2. Wait 5 minutes minimum
3. Discharge capacitor with insulated screwdriver
4. Verify discharge with multimeter
5. Wear insulated gloves

If you are not comfortable with electrical safety procedures, hire a professional. The $100-$250 labor cost is reasonable insurance against electrical injury.

Step-by-Step Replacement

1. Safety First

• Turn off AC at thermostat
• Shut off power at disconnect (outdoor)
• Turn off at circuit breaker (indoor panel)
• Wait 5 minutes

2. Access Capacitor

• Remove outdoor unit access panel (usually one or two screws)
• Locate capacitor (cylindrical, near top)
• Photograph all wiring before touching anything

3. Discharge Capacitor

• Using insulated screwdriver with rated plastic handle
• Touch metal shaft across both terminals simultaneously
• For dual capacitors: discharge C-to-Fan, then C-to-Herm
• Verify with multimeter (should read near zero voltage)

4. Remove Old Capacitor

• Note wire colors and positions (take another photo)
• Disconnect wires (pull-off or unscrew terminals)
• Remove mounting bracket/strap
• Remove capacitor

5. Verify Replacement Part

• Match voltage rating (can go higher, never lower)
• Match capacitance within 10% (exact match preferred)
• Match terminal configuration
• Dual capacitors: match both ratings (e.g., 35+5 μF)

6. Install New Capacitor

• Position in mounting bracket
• Connect wires exactly as documented
  • Common (C) = wire to contactor
  • Herm = wire to compressor
  • Fan = wire to fan motor
• Verify all connections are tight

7. Test System

• Replace access panel
• Restore power at breaker, then disconnect
• Set thermostat to call for cooling
• Verify both fan and compressor start
• Listen for normal operation sounds

Common DIY Mistakes

Wiring Errors:

• Reversing Herm and Fan terminals (won't damage, but won't work)
• Loose connections causing arcing
• Cross-threading terminal screws

Part Selection Errors:

• Wrong voltage rating (too low = fire hazard)
• Wrong capacitance (causes motor issues)
• Buying incompatible form factor

Safety Errors:

• Failing to discharge capacitor (shock hazard)
• Working with power on
• Touching terminals without verification

Professional vs DIY Cost Comparison

DIY Savings: $100-$250 per replacement

When to DIY:

• You're comfortable with electrical work
• You have a multimeter and proper tools
• System is out of warranty
• It's not an emergency (time to research and order parts)

When to Hire Professional:

• Not comfortable with electrical safety
• System is under warranty
• Emergency situation (need same-day repair)
• Uncertain of diagnosis
• Multiple components may be failing

Factors That Affect Capacitor Replacement Cost

1. Capacitor Type

2. Service Call Timing

3. Geographic Location

4. Service Provider Type

Signs You Need Capacitor Replacement

AC Won't Start (Compressor)

Symptoms:

• Outdoor unit hums but doesn't start
• Clicking sound, then nothing
• Breaker trips after attempted start
• Unit tries to start repeatedly, then shuts off

Likely Cause: Failed start or run capacitor for compressor

Fan Won't Spin

Symptoms:

• Compressor runs but fan is stationary
• Fan spins slowly or wobbles
• Fan starts only when manually pushed
• Humming from fan motor area

Likely Cause: Failed fan capacitor (or fan section of dual capacitor)

System Short Cycles

Symptoms:

• AC turns on and off frequently
• Runs for only a few minutes
• Compressor cuts out under load
• Inconsistent cooling

Likely Cause: Weak capacitor not providing enough start power

Visible Capacitor Damage

What to Look For:

• Bulging or domed top (most common sign)
• Brown or rust stains on casing
• Oily residue leaking from bottom
• Melted terminal boots
• Burn marks or scorching

Any visible damage means immediate replacement is needed.

Capacitor Replacement Cost by State

Preventing Capacitor Failure

Regular Maintenance

Annual Tasks:

• Have HVAC technician check capacitor readings
• Keep outdoor unit clean and clear of debris
• Ensure proper airflow (trim vegetation)
• Replace air filters regularly

Every 5 Years:

• Proactively replace capacitors in hot climates
• Check electrical connections for tightness
• Inspect for signs of wear

Power Protection

Recommended Measures:

• Install whole-house surge protector ($300-$600)
• Use HVAC surge protector ($50-$150)
• Consider hard start kit for older systems
• Address voltage issues with electrician

Environmental Factors

Reduce Heat Stress:

• Provide shade for outdoor unit (without restricting airflow)
• Ensure proper clearance around unit
• Keep coils clean
• Avoid running AC during power fluctuations

When Capacitor Replacement Isn't Enough

Signs of Bigger Problems

Capacitor Failed Quickly After Replacement:

• Voltage issues (too high or fluctuating)
• Motor drawing excessive current
• Short cycling damage
• Incorrect capacitor installed

Multiple Component Issues:

• Contactor also failing
• Fan motor drawing high amps
• Compressor struggling to start
• Refrigerant issues present

Consider System Evaluation When:

• Capacitors failing every 1-2 years
• System is over 15 years old
• Multiple repairs in same season
• Cooling capacity has declined
• Energy bills increasing

Getting Quotes and Choosing a Technician

What to Ask

1. "What is the total cost including parts and labor?"
2. "What brand/rating capacitor will you install?"
3. "Is there a warranty on parts and labor?"
4. "Can you test other components while here?"
5. "Do you offer a maintenance plan discount?"

Red Flags

• Significantly higher part prices than online (some markup is normal, 10x is not)
• Pressure to replace entire AC unit for a capacitor issue
• Unable to explain what failed or why
• No written estimate
• Requires full payment before work

Getting Fair Pricing

• Get 2-3 quotes for comparison
• Ask about diagnostic fees that apply to repair
• Check online reviews before calling
• Ask if they stock common capacitors (avoids parts delay)
• Consider annual maintenance agreements for discounts

Conclusion

AC capacitor replacement costs $110-$300 with professional installation, making it one of the more affordable HVAC repairs. The part itself is inexpensive ($10-$50), with labor comprising most of the cost.

For handy homeowners comfortable with electrical safety, DIY capacitor replacement can save $100-$250. The key is understanding the serious shock hazard—capacitors store dangerous charges even when power is off. Proper discharge procedure is mandatory before touching any terminals.

Key considerations when replacing an AC capacitor include matching voltage and capacitance ratings exactly, documenting wiring before disconnecting anything, and recognizing that repeated capacitor failures may indicate larger electrical or mechanical issues requiring professional diagnosis.

For most homeowners, the $100-$250 labor cost for professional replacement is reasonable, especially given the safety risks and potential for misdiagnosis. If you choose DIY, take electrical safety seriously—no repair savings are worth a serious shock injury.