Solar Inverter Oversizing Vs. Undersizing: Pros And Cons

Generally, when choosing a solar inverter for a system, you’d prefer a 5KW solar inverter for a 5KW solar array. This seems right, as both components have equal power specifications. However, in some cases, choosing an inverter of a slightly higher or slightly lower specification is more beneficial than the solar array’s power specification. Let’s first discuss the terms oversizing and undersizing.

If a 5KW solar inverter is connected to a 6.6KW solar array, the inverter’s power specifications are lower than the array, and such an inverter is called an undersized inverter.

Similarly, if a 5KW solar inverter is connected to a 4.9KW solar array, the inverter’s power specifications are higher than the array, and such an inverter is called an oversized inverter.

Undersized Solar Inverter
Undersized systems are useful when you want to generate the maximum power your inverter can. The power generated by a 5KW solar array and 5KW solar inverter never really produces 5KW of power. In fact, it reaches near 4KW only during the peak hours around 12-2 PM.

For most of the day, especially in the morning and evening, the power is far less. This is because a 5KW solar array never generates exactly 5KW as there are certain power losses. Moreover, some power is lost in the cables and connections. And when the inverter processes the power, some power loss occurs in the inverter too. The aggregate power loss is why the array offers less power than 5KW.

But what if you connect an array of a higher specification with the same 5KW solar inverter? Connecting a 6.6KW solar array gives almost up to 5KW of solar power during peak hours. At other times too, the power output is slightly higher than usual.

But you might wonder, what happens during the peak hours when the array generates power higher than the inverter is designed to manage? The inverter simply clips off the power above 5KW. The power curve seems flat on the top during peak hours.

Undersizing solar inverters are useful, but it has some limitations too. The solar array’s power specifications must not exceed 30% more than the inverter’s specifications. Otherwise, it can cause overheating and reduce the solar inverter’s lifespan.

Pros Cons
Provides higher power output Inverter needs higher maintenance as it functions more
Higher inverter output in low light conditions too Reduced lifespan of inverter
Low specification inverter reduces system cost System cannot be expanded with the same inverter

Since undersizing solar inverters restrict system expansion without adding a new inverter, it is suitable only for small-scale applications. For domestic consumers who do not plan on expanding the system soon and want better solar energy production, undersized solar inverters are a suitable solution.

Similarly, oversizing has some pros and cons, but let’s first discuss why oversizing is adopted.

Oversizing Solar Inverter
Oversizing has only one significant benefit; It enables the consumer to expand the system without adding more inverters. For example, if a 5KW solar array is connected to a 6.6KW solar inverter, it is oversized and can process more power than the solar array can produce. If the same system is to be expanded, more solar panels can be added and connected with the same inverter (if it is within the inverter’s compatible range).

Apparently, future expansion of a solar power system is the only benefit oversizing offers. Usually, large-scale commercial consumers oversize their systems when they have plans for future expansion.

Pros Cons
System expansion becomes easier Higher setup cost
Never reaches full potential and hence overheats less often Inverter takes more space
Lesser operation at full potential increases lifespan Higher cost of inverter maintenance

As already discussed, the only benefit oversizing offers is an easy expansion of the system. Another benefit that should be considered is the enhanced lifespan of the inverter. As the inverter never operates at full capacity, it rarely overheats. This not only helps enhance the inverter’s lifespan but also reduces the need for repair and replacement.

But with its only benefit, it also has several disadvantages. In oversized systems, even though the consumer utilizes power according to the solar array’s specification, he cannot utilize the full potential of the inverter.
Similarly, the setup cost exceeds the system’s capability, which makes the system expensive. And with that, the maintenance cost also increases. For these reasons, generally, oversized systems are not preferred.

Final Thoughts
When choosing between undersizing and oversizing, always consider your current and future energy needs. If you do not plan on expanding the system in the near future, go for an undersized system. These systems are more economical and have higher power generation capacity. However, if you are unsure and might have to expand the system, go for an oversized system.