Soft Start vs Hard Start for AC – What’s the Difference?

We’ve all been there—you switch on the air conditioner and a sudden loud noise comes from the indoor unit. You’ve just experienced a hard start, and it’s not something you want to hear! But, what is the difference between soft start and hard start?

In this blog post, we’re going to take a closer look at the two types of starts and discuss their respective pros and cons. We’ll explain how each type of start works and provide helpful tips for maintenance. Read on to learn more about soft start vs hard start for ACs!

Quick Clarification

Soft start involves slowly increasing the voltage in an AC unit to its optimal level, whereas hard start immediately establishes full power. Soft start can help reduce the wear and tear on an AC unit due to less strain caused by the sudden increase in voltage.

What is a Soft Start AC?

A soft start AC is an air conditioner that utilizes a variable-frequency drive (VFD) to gradually increase its voltage and current to the desired levels. This eliminates the surge of power experienced with hard start ACs, which can place stress on equipment and shorten its life. Soft start ACs can be used with various types of motors, including single phase and three-phase motors found in residential, commercial, industrial, and agricultural applications.

Advocates point out that soft starting can save energy by eliminating the high initial current draw of hard start ACs. In addition, they note that not having a surge of power when turning on an air conditioner can help protect components from wear or damage due to sudden spikes of electricity. Soft starts are also often selected for motors in applications where the load is typically greater than the horsepower rating of the motor, such as pumping or conveyor systems.

On the other hand, some argue that soft start ACs are not well-suited for every application. They note that these technologies can introduce additional complexity into the system, which may either raise cost or require extra maintenance due to potential malfunctions or failures over time. Additionally, soft starters can induce additional losses in the system due to resistive heating when in operation.

Just like any technology, there’s no one-size-fits-all solution when it comes to choosing between a soft start AC and a hard start AC. When selecting between these two options it’s important to consider both their advantages and drawbacks in comparison to your unique application. Now let’s take a closer look at what distinguishes hard start ACs from soft starts: what exactly is a hard start AC?

Main Points to Remember

Soft Start ACs utilize a Variable Frequency Drive (VFD) to gradually increase its voltage and current, which can save energy, reduce strain on components, and may be beneficial in applications with loads greater than the motor horsepower. However, they are more complex and may bring additional maintenance or losses due to resistive heating. A Hard Start AC turns on more quickly and does not require the same complexity of components but may cause higher initial current draw. Choosing between the two technologies depends on the unique application.

What is a Hard Start AC?

A hard start is basically an additional device that’s wired into the compressor of your air conditioning system. It assists in shortening the time it takes to start the compressor motor, while also increasing its life span. This device typically consists of a capacitor and a relay that reduce the amount of starting current the compressor motor needs to get going.

There are two schools of thought when it comes to hard start devices. On one side, those who believe they can dramatically extend the life of an AC system and save energy costs over time by reducing inrush current at startup and eliminating many smaller starts per day. Others, however, are less enthusiastic about their benefits and think it’s an unnecessary expense.

Whatever the argument may be, it has been proven that hard start devices can provide a number of important benefits. In order to properly weigh pros and cons, let’s delve into them deeper in our next section on “Pros and Cons of Hard Start Devices”.

Pros and Cons of Hard Start Devices

Hard start devices are an effective solution to managing the start-up of an air conditioning system. These devices, which are usually installed near the AC’s compressor, shorten the starting up time and provide better protection to the electrical components of the system. But with every technology, there can be pros and cons associated with using these devices:


The most significant advantage of using a hard start device is that it reduces the large inrush current that typically occurs when AC systems first turn on. This protects your AC’s compressor from potential failure due to overloads. Hard start devices also detect problems with low voltage or phase imbalances, protecting both motors and compressor from potential failure. Another benefit is that the hard start device helps reduce wear and tear on other components like capacitors and contactors.


Hard start devices may cause additional strain on other components in the air conditioner such as fans, filters, and ductwork. As these devices create higher startup synchronous speed which accelerates total operating speeds, components will have a shorter performance life. Additionally, if the parameters set by the hard start device aren’t correctly adjusted for a given system, over-voltage could occur leading to compressor damage and crashes.

Overall, while hard start devices can be beneficial they need to be properly configured and used alongside other preventative maintenance measures in order to keep all components running smoothly.

To wrap up this section, it’s important to look at the differences between hard start and soft start AC systems before making any decisions related to them. In the next section we will compare soft and hard starting AC Systems in more depth.

Comparing Soft and Hard Start AC’s

When it comes to deciding what type of AC system you want for your home, both a soft start and hard start AC can offer a viable option. The main difference between the two is in their startup process. Soft starts ACs have gradual startup operations that help reduce the electrical demand when they are initially turned on, while hard start AC systems have a much more abrupt and intense startup procedure.

Soft starts bring certain benefits to the table, such as a reduction in peak power demand, less stress on the equipment during initial powering up, lower consumer peak loads as well as an extended motor life. On the other hand, hard starts provide better mechanical power than soft starts in extremely hot climates where the engines need to ramp up quickly in order to adequately cool down a space quickly.

It’s important to consider the various pros and cons of both soft and hard starts ACs when making your decision. If you need an AC solution that provides efficient energy savings and a longer lifespan, then a soft start may be the best choice. On the other hand, if you live in a very hot climate or if you require quick cooling capabilities from your AC system, then a hard start may be more suitable for your needs.

Ultimately, choosing between a soft and hard start depends on many factors such as climate consideration, frequency of use, budget and overall preference for efficiency vs convenience. With all these factors considered, customers can make an informed decision when it comes to selecting between AC’s with soft or hard starts.

Now that we’ve discussed comparing soft and hard start ACs and weighed the advantages of both options, let’s move onto exploring how compressor impacts come into play with each system in our next section.

Compressor Impact

When comparing soft start versus hard start for air conditioning, the compressor impact should be taken into consideration. Compressors play a vital role in maintaining optimal performance of an AC system and must be properly managed to ensure long-term, efficient operation with minimum disruption.

Hard starting can put stress on a compressor as it quickly ramps up to full speed when the AC unit is first turned on. This rapid increase in power load can result in reduced life expectancy of the compressor due to possible overloading or heat damage; whereas a soft starter provides a more gradual increase that helps to protect compressor parts from this kind of damage.

On the other hand, some will argue that a soft starter may have negative implications too. It may cause pulse current levels to increase due to frequent start/stop operations, which could also cause premature failure of parts like bearings and fans on the compressor due to continual vibration caused by the “gripping” of these components.

Ultimately, each application should be assessed on its individual merits and factors to decide whether soft starting or hard starting is most suitable for the compressor. This assessment should take into account previous incidents, like motor failure, and whether there have been any recent updates such as extended motor life expectancy as part of the upgrade process.

Having considered how compressors are impacted by both soft start and hard start AC systems, we now turn our attention to electrical equipment protection when discussing the differences between these two approaches.

  • Soft starter compressors typically consume 20-90% less starting energy compared to a hard starting AC compressor.
  • Soft starters can extend the life of an AC compressor by up to 50%, due to the reduced mechanical stress on the components.
  • A study conducted in 2010 concluded that a soft starter could reduce motor overheating by up to 40%, which significantly improves AC motor longevity.

Electrical Equipment Protection

The way in which AC (Alternating Current) motors are started can have serious implications in terms of power quality, motor torque and protection of related electrical equipment. When AC motors draw large current at startup, other electrical equipment connected to the same power source can be adversely affected due to the high inrush current. A soft start would reduce this damaging inrush current, greatly reducing the risk of damaging expensive or sensitive electronic components or circuitry.

On the other hand, hard starting could provide greater protection for mechanical switchgear and fuses due to lower average current levels during starting. This could prevent damage from arcing or from too many starts within a certain time frame.

No matter which technique is employed, it’s important that together with appropriate motor starters, effective overload protection should be provided to guard against motor failure due to heavy load conditions and/or extended hot running periods.

Overall, both soft starting and hard starting offer potential electrical equipment protection benefits; however proper selection and incorporation of suitable control gear is essential for successful operation with maximum protection for your electrical equipment.

Finally, efficiency and operation must both be considered when deciding which approach is best for your specific application; this will be discussed further in the following section.

Efficiency and Operation

When it comes to the efficiencies of soft starters versus hard starters, there are several areas which must be considered. Soft starters reduce the initial inrush current for a motor start-up by gradually increasing the voltage applied over time. This helps to limit additional stress on both the motor and connected equipment, thus reducing energy losses due to heating and allowing for a more efficient operation overall. Hard starters on the other hand, do not address starting current and instead apply full voltage instantly upon start-up creating a much larger initial power draw from the power source. In addition, hard starters are essentially operating at maximum efficiency once the motor has reached full speed, whereas soft starters can actually help maintain higher operating efficiencies by providing a consistent supply of torque throughout operation.

In terms of reliability of operation, soft starters have an edge over hard starters due to their designed ability to adjust voltage output in response to process changes or other potential issues downstream. This allows them to continue running effectively even when faced with adverse conditions such as power sags or surges. Again, hard starters lack this level of adjustable responsiveness leaving them susceptible to unforeseen operational risks during startup or runtime.

To conclude, when taking operational efficiency and reliability into consideration, soft starters clearly offer significant performance advantages over their hard starter counterparts. With that being said, choosing the right combination of parameters for your application is imperative in order ensure long-term performance optimization.

Having discussed the pros and cons of each type of starter in regards to efficiency and operation we can now move onto discussing how best to choose the appropriate option for your application. In the following section we will discuss the factors that should be taken into consideration when selecting either a soft start or hard start option.

Choosing the Right Soft/Hard Start Option

Choosing the right soft/hard start option for your AC unit can be a daunting task. The two methods both offer advantagesand drawbacks, and understanding which is best for your specific system will require research and analysis.

Soft starts are beneficial because they reduce the strain on electrical motors, allowing them to produce more power in their first few seconds of operation. Hard starts, on the other hand, provide immediate power for a short period of time but can create heat build-up that can cause damage over time.

The right choice will depend on the unique characteristics of your system and its motor. If you have an older AC unit with a less powerful motor, then a soft start would be the better option as it will help extend the life of the unit. However, if you have a modern AC unit with a powerful motor, then a hard start may be more appropriate as it will allow for faster starts and smoother running. Additionally, it is important to consider energy efficiency when selecting your option as soft starts tend to use less electricity overall compared to hard starts.

In order to make an informed decision about which type of start is best for your AC unit, it is important to consult with an expert who has experience in the field and can provide tailored advice related to your specific system. After all, choosing the wrong option could cost you in terms of money and efficiency over time.

Now that we have discussed the pros and cons of both soft/hard start options, let’s move onto some final thoughts regarding these types of AC units in our next section.

Final Thoughts on Soft/Hard Start AC’s

When considering the two types of starting methods for AC systems, it is important to weigh all the factors. Soft start ACs have some advantages over hard start ACs, such as their gentler starting process, quieter operation and improved energy efficiency. On the other hand, hard start ACs are more powerful and can handle larger loads better.

From an energy standpoint, soft start ACs may provide a greater savings in the long run, but that savings could be offset by additional initial costs associated with purchasing and installing a soft start system. Additionally, for large buildings where heavier cooling needs are required, hard start ACs might be a better choice due to their increased power capacity.

All in all, each type of AC has its benefits and drawbacks that need to be carefully considered when making a choice between the two types. Ultimately, the decision should be based on user preference and budget constraints – there is no right or wrong answer.

As far as proper maintenance goes, both types of ACs need regular cleaning and inspection to ensure they are operating at peak performance and safety levels. Doing so will help extend the life of any AC system and keep it running optimally throughout its lifespan.

Answers to Commonly Asked Questions

What is the difference between a soft start and a hard start for an AC unit?

Soft start and hard start are two different methods used to start an AC unit. A soft start gradually increases the voltage and current to the motor, allowing it to ramp up in speed over time. This process is designed to reduce wear on the device and conserve energy. In contrast, a hard start involves immediately providing full voltage and current directly to the motor. While this may help the motor to start up faster, it can also cause more stress and premature wear on the equipment.

In general, soft starts are best for frequent starting or restarting of devices like AC units, while hard starts can be beneficial for applications where getting started quickly is more important. Ultimately, choosing between the two depends on the specific application and user needs.

What are the benefits of a soft start compared to a hard start for an AC unit?

Soft start technology is a relatively new development in air conditioning systems that can provide a number of considerable benefits compared to traditional hard start motors. While traditional hard start motors require an initial surge of electrical current to get their blades spinning, soft start motors can slowly increase current to optimal levels, resulting in smoother and quieter operation and shorter startup times. Additionally, because soft start motors do not have to consume as much power during startup, they often lead to lower energy costs over time.

Soft start technology also offers more reliable starts than hard start motors, since the gradual ramp up of electrical current limits system strain and reduces wear on components. This increased reliability helps prevent repair costs down the line and improves overall performance. Finally, because soft start technology dissipates heat buildup more effectively than hard start motors, these AC units typically require less servicing and run longer without problems.

How does a soft start affect an AC unit’s energy efficiency?

A soft start for an AC unit can improve its energy efficiency by reducing the amount of electricity needed to start the compressor, which is a major energy-consuming component. When a unit uses a soft start, the starting current is slowly increased over time instead of being released in one large burst all at once. This helps reduce power surges, allowing the unit to draw less current and use less energy to kickstart operation. Additionally, using a soft start reduces wear and tear on parts within the compressor as they are slowly introduced to full power after gradual increases over several seconds or even minutes. In the long run, investing in a soft start will help increase energy efficiency while also decreasing maintenance costs due to less strain on system components.

Are there any drawbacks to using a soft start for an AC unit?

The primary drawbacks of using a soft start for an AC unit compared to a hard start are the added complexity of installation, cost and size. Soft start technology requires additional components that can be costly to install and require more space than a traditional hard start starter motor and capacitor. Additionally, the circuitry in a soft start AC unit can become damaged over time if it is not properly maintained, resulting in higher repair costs. Finally, soft start AC units tend to take longer to reach peak performance levels due to their slower ramp-up time than hard start AC units.

Key Questions:

A key question to consider when comparing soft start and hard start for AC is which type will provide the most efficient performance. When it comes to efficiency, soft start has the edge over hard start. Soft start uses a slower, more gradual approach to ramp up power by slowly increasing voltage, minimizing initial power draw. This ensures that any current spikes associated with a hard start are avoided and can help prolong the life of the motor and batteres. Additionally, as less power is drawn at once, overall electrical costs may be reduced. There are also safety concerns to consider with a hard start since high-current surges can potentially damage delicate wiring or other components in your AC system.

On the other hand, some may argue that a hard start is more reliable than a soft start. Hard starts are often more reliable because they rely on mechanical parts rather than electronic components. Therefore they tend to be simpler and less prone to failure compared to their electronic counterparts. However, if you choose a hard start solution it’s important to ensure it can handle the load current required by your AC system as failure to do so could lead to motor problems or even fire hazards.

Overall, when considering the efficiency and reliability of soft start vs hard start for AC systems, it’s important to weigh all of the pros and cons carefully. If you choose to go with a soft start solution, make sure you pick one that is rated for high-power AC equipment and offers steady voltage control throughout operation. In this way, you can be assured of an efficient and safe operation for your AC system.