As an HVAC expert, you are quite aware of one of the most crucial components within the outdoor unit of an air conditioner system, the capacitors. 

It is more like a cylindrical battery that is responsible for channeling power to the motors of an AC system. They run when the compressor is signaled to operate to cool down the property.

The experts you hire for servicing the air conditioning system will primarily check the capacitors for seamless functionality. It is because if the capacitor malfunctions, then the operation of an entire HVAC system fails. 

So, whether you are learning to start a new HVAC business or want to know how an AC capacitor works, this article is for you. 

What is an HVAC Capacitor?

In electrical terms, it is the storehouse for energy within the electrostatic field. The purpose of an AC capacitor is to stabilize the voltage consumed by the HVAC system to function seamlessly. 

The major HVAC motors, such as blowers, outdoor fans, and compressors, have their capacitor pair (start and run capacitors). The purpose of the first capacitor is to help ignite the motor, while the other in the pair helps keep the motor running to serve the purpose. 

In simple language, HVAC capacitors of an AC unit store electricity and function as a form of rechargeable battery. Thus, this battery powers the connected motor with the required energy to maintain the operational flow. 

Not just the AC unit but even the heating systems, such as the heat pump, have dual capacitor setups to bridge the energy gap between the compressor and the blower. Furnaces, on the other hand, use a single-run capacitor that connects to the blower motor. 

What Does an AC Capacitor Do?

After knowing the definition, you probably have an idea of how it functions with the air conditioning or HVAC system. The initial jolt of electricity is triggered by the start capacitor to initiate the motor. And then, the run capacitor maintains the flow of that energy. 

The energy sent to the AC system’s motors is in burst mode. These bursts rev up the motor to kick-start its cooling cycle. When the cooling system is functional, the start capacitor will then work on reducing the energy output, but the run capacitor continues to supply a steady flow of current till the cooling cycle ends. 

The AC capacitors are measured in units of microfarads and voltage. Voltage measurement shows the amount of current flowing through a capacitor. The higher the voltage, the faster the current flows through it. Microfarad measurement determines the current-storing potential of a capacitor. 

AC capacitors might resemble the functionality of batteries, but they are practically connected to the wiring board of your AC system. Therefore, unlike some appliances, it is not safe for homeowners to take the replacement job into their own hands. AC capacitors are high-voltage devices that can seriously harm rookies.

Types of AC Capacitors

Depending on the type of air conditioner, there is a possibility that an HVAC system might have two single capacitors or a dual capacitor. To help you with a better understanding of the facts, here is a detailed understanding of both of these types and their functionalities:

1. Single capacitors

The air conditioner, which requires two single capacitors, must include a start capacitor and a run capacitor. As stated earlier, the start capacitor initiates the energy delivery to the motor and stops functioning. The run capacitor then kicks in and maintains the flow of energy to keep the AC blowing.

2. Dual capacitors

As the name suggests, dual capacitors are a combination of start and run capacitors in a single unit. The same capacitor initiates the spark and then supplies a consistent flow of balanced energy to keep the AC system running. A dual capacitor offers much more significance than a single capacitor. Moreover, using it will save space within the HVAC system, and replacement is also easier.

Apart from these two commonly preferable capacitors, there are a few other varieties in electrical terms that make a difference in terms of their utilization. They are:

  • Ceramic capacitors- These capacitors are used as the bypass capacitors for bypassing the high-frequency content of the air conditioner circuit. It protects the sensitive circuitry of an air conditioner due to high-frequency noises. 
  • Electrolytic capacitors- These capacitors are useful in smoothening the DC voltage for your air conditioning unit after voltage rectification by diodes. In simple words, it reduces the DC supply ripples or hiccups. 
  • Safety capacitors- Such capacitors are used in the inverter control circuitry of air conditioners. Resistors are used along with these capacitors to pull off the charge from them after the system is turned off. 

Factors in Calculating AC Capacitor Replacement Cost

When in an HVAC business, you will have to attend to the calls or service requests for malfunctioning air conditioning systems. The first thing you or your HVAC technician will check is the need for a new capacitor. You must know the AC capacitor replacement cost of it to be able to serve your customers and bring in profit to your HVAC business

So, how are you planning to calculate the AC capacitor replacement cost, and what is included in your service estimate? Here are some factors that contribute to calculating the cost of an air conditioner capacitor and its replacement estimate:

1. Type of unit

Air conditioner capacitors and heat pump capacitors, both are different in terms of their functionalities. So, the cost also differs for them. Heat pump capacitors are quite expensive in comparison to the AC capacitor replacement cost.

Specifically for AC units, there are different makes and models that can affect the cost of a capacitor. Large AC units need high potential capacitors, whereas moderate units need standard ones. With higher potential, the cost of capacitors also increases. 

Apart from that, standard capacitors are easy to install, for which the labor cost will also be less for your business. As a result, you will be making good profits with the price you quote. 

2. Type of capacitor

As stated in the previous section, there are different types of capacitors necessary for specific units, as chosen by the manufacturers, to meet the functional potential of the entire system. The cost of single capacitors is around $10 each of them. If a system is compatible with the same, then a maximum of $20 will be the cost for a replacement pair of capacitors.

Dual capacitors are more functional and optimized components that cost up to $50. The price is variable for different makes and models, depending on the exact needs of an AC unit.

3. Challenges in diagnosing a problem

For some specific capacitor problems, the symptoms are not always clear for an HVAC technician. In some cases, if the HVAC system stops after making a humming noise, it is a sign of a failing AC capacitor

But, in some specific cases, the unit keeps running intermittently, or the fan keeps running, without producing cool air. In such cases, your technician cannot directly determine the fault of its capacitor, as there might be other possible reasons to trigger such symptoms. 

The technicians might have to diagnose a lot of possibilities in an AC unit before coming to a conclusion on faulty capacitors. In such cases, the effort is also chargeable as the new AC capacitor replacement cost.

4. Warranty 

In an HVAC business, you must commit with assurance to the customers in order to make sure they trust you for a long time. Most HVAC companies offer a warranty on capacitors, resistors, and other components they have installed or replaced for a customer. 

So, if the AC capacitor breaks down within the warranty period, your company should take charge and replace it free of cost. It is because your commitment to assurance should be justified. Therefore, it is advisable for companies to use quality capacitors to avoid losing money on warranty claims.

5. Seasonal pricing

In the summer months, when people use AC units relentlessly, the chances of capacitors wearing out increase. Therefore, your HVAC company might be in high demand. So, it is that time of the year when you can charge premium pricing from your customers. 

You can schedule an upfront visit to your existing customers and offer them seasonal maintenance at an affordable cost to prevent high replacement and service costs in the long run. You can suggest them if the capacitor is already wearing out and install a replacement capacitor to grow your business and earn customer satisfaction. 

How Much Does an AC Capacitor Cost?

The average cost of an AC capacitor ranges between $9 and $25. But, as a professional, you can charge around $60 to $200 for its installation in the central air unit. Your service cost will depend on the above factors and many other such considerations such as overheads, profit margin, and others.

Frequently Asked Questions

What are the signs or symptoms of a faulty AC capacitor?

If the customer shares any of the below signs and symptoms of their air conditioner unit, you can conclude that they have a faulty capacitor: 

  • AC is not kicking off the cooling cycle 
  • AC shuts down all by itself. 
  • Cool air is not flowing through the indoor unit even when the AC is on
  • Experiencing a humming noise while AC is in running state
  • Higher energy bills than usual
  • Burning smell or visible smoke from AC unit

If these are the symptoms being conveyed to you by your customers, ask them to shut down the HVAC system and wait for your technician to arrive.

What is the lifespan of an AC capacitor?

The usual lifespan of an AC capacitor is between 10 to 20 years. Hence, this is the reason why technicians do not primarily check the capacitors in case of indirect symptoms of malfunctions in your AC unit. It is because they expect the capacitors to last longer than other vital components.

Unless the AC unit is experiencing operational stress, the AC capacitor won’t be overloaded with energy needs and will last longer.

Are all the AC capacitors the same?

There are different AC capacitors installed across different parts of an entire air conditioning system. Some of them include various run capacitors for motors of compressors, outside fans, indoor fans, and start capacitors.

The most common AC capacitor that often fails and demands replacement is the run capacitor for the compressor motor.

Can you interchange start and run capacitors for an AC unit?

Start and run capacitors have their own differences, for which they have been categorized differently. Using a run capacitor at the place of a start capacitor or vice versa will short out the AC unit. As a result, it will adversely impact the fan or compressor motor.

What will happen if you are using the wrong capacitor for an AC unit?

If you choose the wrong capacitor for your AC unit, then the motor will lack sufficient magnetic field. As a result, the rotor will hesitate to function seamlessly at uneven spots. Such a lack of functionality will trigger the motor to be noisy and increase electrical energy consumption. The performance will drop, and the motor will overheat, causing other functional problems in the entire unit.


Customers are free to buy a new AC capacitor if they know how to pick the right one for the job. But, without electrical knowledge, it is not safe for homeowners to approach the replacement job all by themselves.

Therefore, be clear with your customers whether they want you to get a new capacitor or if they already have the set. If they insist on buying the correct capacitor from their end to be assured of saving some costs, then help them with the specifications on their request. 

Depending on the initial discussion, you can plan your AC repair or capacitor replacement price quotation and send it to your potential customers.