Do Capacitors Go Bad if Not Used?

Do Capacitors Go Bad if Not Used?

Capacitors are essential components used in a wide range of electronic devices and systems. However, in certain situations, capacitors may be left unused for extended periods. This raises the question: Do capacitors go bad if not used? The answer is not straightforward, as various factors come into play.

While some types of capacitors can maintain their functionality over long periods of inactivity, others may experience degradation or loss of performance. In this article, we will explore the effects of non-usage on capacitors, factors that can contribute to their deterioration, and recommendations for ensuring the longevity of unused capacitors.

Construction of Capacitors

Capacitor Basics

Before delving into the construction details, let’s briefly review the fundamental principles of capacitors. Capacitors consist of two conductive plates separated by a dielectric material. When a voltage is applied across the plates, an electric field is created, which stores electrical energy.

The capacitance, measured in farads (F), determines the amount of charge a capacitor can store per unit of voltage [1].

Construction of Capacitors

Components of Capacitors

Conductive Plates

The conductive plates are the primary components of a capacitor. These plates can be made of various conductive materials, such as aluminum, tantalum, or ceramic. They are typically thin and flat, with a large surface area to maximize capacitance. The conductive plates serve as terminals for connecting the capacitor to an electrical circuit.

Dielectric Material

The dielectric material is placed between the conductive plates and acts as an insulator. It prevents direct contact between the plates while allowing the electric field to form. The dielectric material plays a critical role in determining the capacitance and other characteristics of the capacitor. Common dielectric materials include ceramic, polyester, tantalum oxide, and electrolytic solutions.

Types of Capacitors:

  • Electrolytic capacitors have a high capacitance and are often used in applications requiring large energy storage. They consist of two conductive plates submerged in an electrolyte solution, with a dielectric oxide layer formed on one of the plates. The electrolyte provides the necessary ions for the formation of the oxide layer;
  • Ceramic capacitors are compact and widely used in electronic circuits. They are constructed using a ceramic material as the dielectric. The conductive plates are often made of a thin metal layer applied to the surface of the ceramic material. Ceramic capacitors come in various shapes and sizes, including disc, chip, and multilayer configurations;
  • Film capacitors utilize a thin polymer film as the dielectric material. These capacitors offer excellent stability, low losses, and high reliability. They are available in different film types, such as polyester, polypropylene, and polycarbonate. Film capacitors are commonly used in applications requiring precision and high-performance characteristics [2];

Construction Process

The construction process of capacitors can vary depending on the type and size. However, the basic steps involved in their manufacturing include:

Construction of Capacitors

Plate Preparation

The conductive plates are manufactured by shaping the chosen conductive material into thin sheets or films. The surface is often treated to enhance its properties, such as roughening or coating.

Dielectric Application

The dielectric material is applied to one or both sides of the conductive plates. This can be done through processes like coating, deposition, or impregnation, depending on the type of capacitor.

Plate Stacking

Multiple conductive plates with dielectric layers are stacked together to increase the surface area and hence the capacitance. They are carefully aligned and separated by spacer materials to maintain the desired separation distance.


The stacked plates are enclosed within a protective casing made of materials like plastic, metal, or ceramic. This casing provides insulation, mechanical support, and environmental protection.

Terminal Attachment

The conductive plates’ terminals are connected to the external leads or terminals of the capacitor, allowing for easy integration into electrical circuits. Terminal attachment methods can include soldering, welding, or crimping.

Shelf Life and Storage of Capacitors:

1) Aluminum Electrolytic Capacitors

Aluminum electrolytic capacitors are widely used due to their high capacitance and energy storage capabilities. However, they have a limited shelf life compared to other capacitor types. The electrolyte within these capacitors gradually dries out over time, leading to a decrease in performance.

To maximize the shelf life of aluminum electrolytic capacitors, it’s important to store them under appropriate conditions. These capacitors should be kept in a cool and dry environment with a temperature range typically between -40°C (-40F) to +85°C (185F) [3].

Shelf Life and Storage of Capacitors:

Exposure to high temperatures can accelerate the drying out of the electrolyte and shorten their shelf life.

Additionally, it is advisable to store them in their original packaging or anti-static bags to protect them from moisture and potential electrostatic discharge.

2) Tantalum Capacitors

Tantalum capacitors are known for their compact size, high reliability, and stable performance. They have a relatively long shelf life compared to aluminum electrolytic capacitors. Tantalum capacitors use a solid electrolyte, which contributes to their durability and resistance to drying out.

To ensure the longevity of tantalum capacitors, it is recommended to store them in a cool and dry environment with a temperature range typically between -55°C (-67F) to +125°C (257F) [4]. Similar to aluminum electrolytic capacitors, protecting tantalum capacitors from moisture and electrostatic discharge is essential. Storing them in their original packaging or anti-static bags can help maintain their quality.

3) Ceramic Capacitors

Ceramic capacitors are versatile and commonly used in various electronic applications. They have a relatively long shelf life and are less prone to drying out compared to electrolytic capacitors. However, their capacitance can slightly decrease over time due to aging effects.

For optimal storage of ceramic capacitors, it is recommended to keep them in a dry environment with a temperature range typically between -55°C (-67F) to +125°C (257F). Protecting them from moisture and extreme temperature fluctuations is crucial. Storing them in anti-static bags or their original packaging can provide additional protection.

Factors That Can Cause Damage to Capacitors:


Capacitance, measured in farads (F), is a fundamental property of capacitors that determines their ability to store electrical charge. Factors that can affect capacitance include aging, temperature changes, and manufacturing variations. Significant deviations in capacitance from the specified value can impact the functionality of circuits and devices.


Humidity, the presence of moisture in the surrounding environment, poses a risk to capacitors. Moisture can penetrate the capacitor’s enclosure and affect its internal components, such as the dielectric material or the electrodes. This can lead to a decrease in capacitance, an increase in leakage current, and even short circuits. Proper sealing and storage in low-humidity environments are crucial to protect capacitors from moisture damage.

Factors That Can Cause Damage to Capacitors:

High Temperatures

Exposure to high temperatures can cause damage to capacitors. Elevated temperatures can accelerate the drying out of electrolytic capacitors, leading to a decrease in capacitance and an increase in equivalent series resistance (ESR). Ceramic capacitors may experience a reduction in capacitance or shift in their electrical characteristics under extreme temperature conditions.

Adhering to the recommended temperature ranges and providing adequate cooling are essential to prevent heat-related damage.

Life In Service

Capacitors have a limited operational lifespan, which can vary depending on the type and usage conditions. Over time, factors such as aging, voltage stress, and temperature cycling can lead to degradation in capacitance, increased leakage currents, and reduced reliability. Understanding the expected lifespan of capacitors and implementing appropriate replacement strategies can help prevent unexpected failures.

Dissipation Factor

The dissipation factor, also known as the tangent of the loss angle or the power factor, measures the energy losses in capacitors. High dissipation factors can result from dielectric losses or ESR. Excessive dissipation factors can lead to heating, reduced efficiency, and decreased lifespan of capacitors. Choosing capacitors with low dissipation factors and avoiding conditions that contribute to increased losses are crucial for maintaining optimal performance [5].

Insulation Resistance

Insulation resistance measures the ability of the dielectric material to resist the flow of leakage current. Lower insulation resistance values can indicate the presence of moisture, contamination, or dielectric breakdown. Monitoring insulation resistance and ensuring proper sealing and storage conditions are vital to prevent leakage currents and potential damage to capacitors.

Sealing Quality

The sealing quality of capacitors plays a significant role in protecting them from external elements such as moisture, dust, and contaminants. Poor sealing or compromised enclosures can result in accelerated degradation, reduced capacitance, increased leakage currents, and even catastrophic failures. Employing high-quality sealing techniques and maintaining appropriate storage conditions are critical for preserving the integrity of capacitors.

Dielectric Strength

Dielectric strength refers to the ability of the dielectric material to withstand high voltages without breaking down. Exceeding the specified voltage ratings can cause dielectric breakdown, leading to short circuits or permanent damage to the capacitor. Adhering to voltage ratings, implementing proper voltage derating practices, and avoiding voltage spikes are essential to protect capacitors from dielectric failure.

Factors That Can Cause Damage to Capacitors:

Vibration And Shock

Mechanical stress, such as vibration and shock, can impact the structural integrity and electrical characteristics of capacitors. Excessive vibrations can cause lead fractures, internal disconnections, or even detachment of electrodes. Mechanical stress can also lead to changes in capacitance or electrical parameter shifts. Mounting capacitors securely, using appropriate vibration-damping techniques, and considering the mechanical stress limits during product design are vital to prevent damage.

Barometric Pressure

In certain applications, such as aerospace or high-altitude environments, barometric pressure variations can affect capacitors. Extreme pressure changes can cause changes in capacitance, leakage currents, or even rupture of the enclosure. Selecting capacitors rated for high-pressure environments and implementing appropriate sealing and protection measures are essential for reliable performance.


In radiation-intensive environments, such as nuclear power plants or space missions, capacitors can be subjected to ionizing radiation. Ionizing radiation can lead to degradation of the dielectric material, increased leakage currents, and changes in electrical characteristics. Choosing radiation-tolerant capacitors or implementing shielding measures can help mitigate the impact of radiation on capacitors.

How Can You Tell If A Capacitor Is About To Fail?

There are several ways to tell if a capacitor is about to fail. Here are some common signs to look out for:

  • Visual indications: If a capacitor is about to fail, it may bulge or leak. The top and bottom are supposed to be flat if it’s a metal canned one;
  • Humming noise: If you hear a humming noise coming from your AC or motor, it may be a sign of a failing capacitor;
  • Hesitation to start: If your AC or motor is hesitant to start, it may be due to a failing capacitor;
  • Age: An aging HVAC system or motor can also be a sign that the capacitor is about to fail;

If you suspect that your capacitor is failing, it is important to have it inspected and tested by a qualified professional to prevent any further problems.

How Can You Tell If A Capacitor Is About To Fail?

Minimizing The Risk Of Capacitor Failure

To minimize the risk of capacitor failure, you can do several things:

  • Choose quality components: It is important to choose high-quality capacitors from reputable manufacturers. These components are more likely to be reliable and to have a lower risk of failure;
  • Use the right type of capacitor for the job: Capacitors come in many different types and sizes, each with specific performance characteristics. Using the right type of capacitor for the job can reduce the risk of failure;
  • Proper application: Use capacitors in accordance with the manufacturer’s instructions, and in compliance with the relevant safety standards;
  • Regular maintenance: Regular preventive maintenance can help detect any issues before they become bigger problems;
  • Reforming large capacitors: Large aluminum electrolytic capacitors can deteriorate over time, so reforming these capacitors can help extend their lifespan and reduce the risk of failure;

By following these guidelines, you can minimize the risk of capacitor failure and ensure the reliable operation of your equipment and systems.

How Long Do Capacitors Last For If Used?

The lifespan of capacitors depends on various factors such as quality, usage, and type. The typical lifespan of an electrolytic capacitor used in electronic devices is around 2,000-10,000 hours [6]. For AC capacitors used in HVAC systems and other similar application, they can often last up to 20 years or more.

How Long Do Capacitors Last For If Used?

However, the lifespan of a capacitor can be reduced if it is exposed to high temperatures or subjected to frequent use.

Regular preventive maintenance can help ensure the capacitors are operating within their designed limits and can help detect any issues before they become bigger problems.

Ultimately, the lifespan of a capacitor depends on the specific application and the environmental conditions it is operating under, so it is important to consult with a qualified professional for specific recommendations.

How Long Do Capacitors Last For If Not Used?

If capacitors are not used, their lifespan can vary widely depending on the type and quality of the components. In general, electrolytic capacitors have a maximum shelf life of approximately 2 years, after which their internal electrolyte can dry out and degrade.

Ceramic capacitors, on the other hand, can last for decades if stored in the right conditions. Other types of capacitors, including film capacitors and tantalum capacitors, have diverse storage lifespans.

However, it is important to note that capacitors are designed to be used within certain time frames and conditions, and storage outside these parameters can affect their overall lifespan and performance. It is recommended to consult the manufacturer’s datasheet for specific information regarding the expected storage lifetimes of capacitors.

How Long Do Capacitors Last For If Not Used?


1. How do you prevent a capacitor from failing?

To prevent a capacitor from failing, several measures can be taken:

  • Proper selection: Choose capacitors that meet the requirements of the application, considering parameters such as capacitance, voltage rating, temperature range, and expected lifespan;
  • Adequate voltage derating: Operate capacitors within their voltage ratings and apply a safety margin by using capacitors with higher voltage ratings than necessary;
  • Temperature management: Ensure capacitors are operated within the specified temperature range and implement appropriate cooling mechanisms to prevent overheating;
  • Minimize mechanical stress: Use proper mounting techniques and consider mechanical stress factors such as vibration and shock to minimize stress on the capacitors;
  • Shielding and filtering: Implement shielding and filtering techniques to protect capacitors from electromagnetic interference (EMI) and radio frequency interference (RFI);
  • Prevent moisture ingress: Employ proper sealing and encapsulation techniques to protect capacitors from moisture and ensure they are stored in dry environments;
  • Regular inspection and maintenance: Conduct periodic inspections to detect any signs of degradation or damage and replace capacitors as needed [7];

2. How many years can a capacitor last?

The lifespan of a capacitor can vary depending on various factors, including its type, quality, operating conditions, and usage patterns.

On average, electrolytic capacitors and tantalum capacitors can last around 1,000 to 10,000 hours.

Ceramic capacitors typically have a longer lifespan, ranging from 50,000 to 200,000 hours. However, it’s important to note that these are general estimates, and specific capacitors may have different lifespan specifications.

3. What are 3 common faults with capacitors:

  • Capacitor leakage: Capacitors can develop leakage currents due to aging, excessive voltage stress, or environmental factors. Leakage currents can reduce the effectiveness of capacitors and affect the overall circuit performance;
  • Capacitor short circuit: A short circuit occurs when the dielectric material inside the capacitor breaks down, causing a direct connection between the terminals. This leads to a loss of capacitance and can potentially damage the circuit;
  • Capacitor open circuit: An open circuit happens when the internal connection between the capacitor’s electrodes is severed, resulting in a complete loss of capacitance and functionality;

4. Can a faulty capacitor damage a motor?

Yes, a faulty capacitor can damage a motor. In motor applications, capacitors are often used to provide an initial boost of energy to start the motor.

If the capacitor is faulty or fails, it may not provide the necessary energy, leading to motor starting issues or decreased performance. In some cases, a faulty capacitor can cause overheating or even motor failure.

5. Can you fix a blown capacitor?

In most cases, a blown or physically damaged capacitor cannot be repaired and needs to be replaced. Blown capacitors typically indicate severe internal damage or a complete breakdown of the dielectric material, making them irreparable. It’s important to follow proper safety protocols and consult a professional when dealing with blown capacitors.

6. How often does a capacitor go bad?

The frequency at which capacitors go bad can vary depending on several factors, including the type of capacitor, operating conditions, and quality. In general, capacitors are designed to have a certain lifespan and are expected to function within specified parameters during that time.

However, external factors such as temperature, voltage stress, humidity, and mechanical stress can accelerate capacitor degradation or failure. Regular inspections, proper maintenance, and adhering to manufacturer guidelines can help identify and address capacitor issues before they lead to complete failure.

7. What does a failing capacitor sound like?

A failing capacitor may produce a buzzing, humming, or crackling sound. This sound is often associated with excessive electrical discharge or arcing within the capacitor. It’s important to note that the sound alone may not be a definitive indicator of capacitor failure, and other diagnostic methods should be employed to confirm the issue.

8. Which is the most common reason for capacitor failure?

Heat is one of the most common reasons for capacitor failure. Elevated temperatures can accelerate the degradation of dielectric materials, increase leakage currents, and affect the overall performance and lifespan of capacitors. Heat-related failures can be mitigated by proper temperature management, including cooling techniques and operating capacitors within their specified temperature ranges.

9. Will the compressor run if the capacitor is bad?

If the capacitor responsible for starting the compressor in a motor-driven system is faulty or fails, the compressor may not start or have difficulty starting. The capacitor provides the initial energy boost required to overcome the motor’s inertia and initiate rotation. Without a functioning capacitor, the compressor may not receive sufficient power to start, resulting in compressor failure to run or insufficient performance.

10. Are capacitors expensive to replace?

The cost of replacing a capacitor can vary depending on its type, capacity, voltage rating, and specific application. Generally, smaller capacitors used in consumer electronics tend to be less expensive, while larger capacitors used in industrial or high-power applications can be more costly. However, the overall cost of replacing a capacitor is relatively lower compared to the potential damage or system failure that can occur if a faulty capacitor is not addressed promptly.

11. How long does an unused capacitor last?

Unused capacitors, if stored properly in suitable conditions, can have a longer shelf life. Electrolytic capacitors, for example, can last for several years if stored in a dry environment with stable temperatures. However, it’s important to periodically inspect and test unused capacitors before use to ensure they are still within their operational parameters.

12. How do you know if a capacitor is still good?

To determine if a capacitor is still functional, several methods can be employed:

  • Visual inspection: Check for signs of physical damage, such as bulging, leakage, or discoloration;
  • Capacitance testing: Use a multimeter or specialized capacitor tester to measure the capacitance. Compare the measured value with the capacitor’s specified capacitance;
  • ESR (Equivalent Series Resistance) measurement: Measure the ESR of the capacitor using an ESR meter. Higher-than-normal ESR values can indicate capacitor degradation;
  • Leakage current testing: Measure the leakage current using a suitable instrument. Excessive leakage currents can indicate capacitor deterioration [8];

It’s important to refer to the manufacturer’s guidelines and consult technical resources when performing these tests to ensure accurate results.

13. What is the average lifespan of a capacitor?

The average lifespan of a capacitor can vary significantly depending on factors such as type, quality, operating conditions, and usage patterns.

As a general guideline, electrolytic capacitors and tantalum capacitors can have lifespans ranging from 1,000 to 10,000 hours.

Ceramic capacitors tend to have longer lifespans, typically ranging from 50,000 to 200,000 hours. These figures are estimates and should not be taken as definitive values for all capacitors.

14. What happens when capacitors get old?

As capacitors age, they can undergo various changes that affect their performance. The dielectric material inside capacitors can degrade, leading to decreased capacitance, increased leakage currents, and reduced overall functionality.

Additionally, aging capacitors may have higher equivalent series resistance (ESR) values, resulting in increased power losses and reduced efficiency. Over time, these changes can impact the performance and reliability of electronic systems.

15. Can capacitors last 40 years?

While some capacitors may have lifespans of 40 years or more, it is essential to note that this depends on multiple factors, including the type of capacitor, operating conditions, and quality. Electrolytic and tantalum capacitors generally have shorter lifespans compared to ceramic capacitors. Longevity can be improved by operating capacitors within specified limits, adhering to proper storage conditions, and implementing appropriate maintenance practices.

16. Do capacitors dry out?

Electrolytic capacitors, which contain a liquid electrolyte, can dry out over time if not properly stored or operated. The drying out of electrolytic capacitors leads to a loss of capacitance and a decrease in their effectiveness. Ceramic and tantalum capacitors, on the other hand, do not “dry out” since they do not contain liquid electrolytes.

17. Do electrolytic capacitors degrade over time?

Yes, electrolytic capacitors can degrade over time. Factors such as temperature, voltage stress, and aging of the electrolyte can lead to degradation of the electrolytic capacitor’s dielectric material. This degradation can result in reduced capacitance, increased leakage currents, and a decrease in overall performance.

18. Can a capacitor go bad in 2 years?

Yes, a capacitor can go bad within a span of 2 years, although this can depend on various factors such as quality, operating conditions, and usage patterns.

If a capacitor is subjected to excessive heat, voltage stress, or environmental factors, it can experience accelerated degradation or failure, leading to a shorter lifespan.

19. Can you reuse old capacitors?

Reusing old capacitors is generally not recommended. Capacitors are subject to aging, and their electrical characteristics can change over time. Additionally, if a capacitor has experienced physical damage or has been in operation for an extended period, its reliability and performance may be compromised. It is best to replace old capacitors with new ones to ensure optimal functionality and reliability.

20. How do you revive a dead capacitor?

Reviving a dead capacitor is generally not possible. If a capacitor has completely failed or is physically damaged, it is best to replace it with a new one. Attempting to revive a dead capacitor can be unsafe and may result in further damage to the circuit or system.

21. How do you rejuvenate a capacitor?

Rejuvenating a capacitor is not a common practice and may not yield reliable results. Capacitors degrade over time due to various factors, including the aging of dielectric materials. Once a capacitor has degraded or experienced significant deterioration, rejuvenation methods are unlikely to restore its original performance. It is advisable to replace degraded capacitors instead of attempting rejuvenation.

22. What are the signs of a weak capacitor?

  • Decreased capacitance: If a capacitor is no longer able to hold its specified capacitance value, it may be considered weak;
  • Increased ESR: A weak capacitor can have a higher-than-normal equivalent series resistance (ESR) value, resulting in power losses and reduced efficiency;
  • Leakage current: Excessive leakage current can indicate a weak or deteriorating capacitor;
  • Bulging or physical damage: Visible signs of physical damage, such as bulging or leaking electrolyte, can be indicative of a weak or failing capacitor [9];

23. How long do capacitors hold a charge?

The time a capacitor holds its charge depends on various factors, including capacitance, load resistance, and leakage current. Capacitors discharge over time, and the rate of discharge is determined by the RC (resistance-capacitance) time constant of the circuit [10]. In general, capacitors can hold a charge for a significant amount of time, ranging from a few seconds to several hours or more, depending on the specific conditions and parameters of the circuit.

24. Is it safe to test a capacitor with a multimeter?

Testing a capacitor with a multimeter can be safe if the proper precautions are taken. Before testing, it’s important to discharge the capacitor fully to prevent electric shock. Additionally, it’s crucial to select the appropriate range and setting on the multimeter to avoid potential damage to the device or inaccurate readings [11]. Following safety guidelines, such as using proper personal protective equipment and observing safe handling practices, is essential when working with capacitors.

25. Do capacitors lose charge over time?

Yes, capacitors can lose their charge over time due to leakage currents. Even though capacitors are designed to store charge, they are not perfect insulators, and a small amount of current can leak across the dielectric material. This gradual discharge leads to a loss of charge over time. However, the rate of discharge depends on factors such as the capacitor’s capacitance, leakage current, and the resistance of the circuit in which it is connected.

Useful Video: When capacitors go bad.