Solar Inverter Sizing - 3 Step Process In Inverter String Sizing

Solar Inverter Sizing – 3 Step Process in Inverter String Sizing

Solar Inverter Sizing
Solar Inverter Placement with Solar Panels

Solar inverters are one of the most critical components of the entire solar panel system. They are primarily responsible for converting Direct Current electricity from the solar panels to Alternating Current (AC) electricity[1] for powering the appliances. 

When you are designing the entire system, solar inverter sizing becomes a crucial factor in the overall production of electricity. Solar Inverter Sizing is essential for completing the overall solar installation, whether small or big. 

The solar energy system over your property is about to produce and send DC electricity to the inverter. Therefore, you should consider solar inverter sizing to handle the implemented load and convert it to AC power.

Therefore, you need to know how to size the inverter properly. But before that, you need to know the rating of an inverter and other aspects before deciding on purchasing a specific inverter. This article will help you complete clarity on all aspects of solar inverter sizing.

 Rating Measures Of A Solar Inverter

Inverter Rating Measures

Solar inverters produce current as they produce it under different conditions.  Here are a couple of ways with which the solar inverters are rated:

The first and most common way the inverters are rated is in Continuous watts or watts ratings. 

#1 Continuous Watt Rating

Continuous watts are defined as the total amount of watts that the inverter can support. For instance, a 2000 watt of the inverter can power around 2000 continuous watts or 2 kW. The bigger size of the solar inverter can handle more power and load. 

If you want the solar inverter to be ideal for your system, the inverter’s watts rating should be the same as that of the watts rating of the solar power system. Hence, this is ideal for ensuring solar inverter sizing for your entire system. 

#2 Surge Watt Rating

Another way with which the solar inverters are rated is the Surge Watts. Surge Watts is defined as the power rating that the inverter can support for a short time. For instance, a 2000 watt solar inverter size, rated at 4000 surge watts, can handle power rating up to 4000 watts for a short period. 

Hence, you might apply these inverters in starting some high power mechanisms such as motors. The motors demand a higher power than usual for getting ignited or started. 

For the inverter size to be perfect for your solar panels and entire system, the surge watts rating must be equal to or higher than that of the potential surge watts of each appliance. 

You can check the surge watt specification on the sticker placed at the back of your appliances. You will need around 1.5 or 2 times more surge watts than continuous watts to ensure a good measure of surge protection. 

This surge watt consideration becomes more essential if you power any heavy-duty equipment with the system. 

#3 Input Voltage Rating

The following rating that determines if the sizing of the solar inverter is acceptable for your system or not is the input voltage. 

The inverter’s input voltage will depend upon the watt or power rating of the inverter. For all the inverters with small power output such as 100 watts, the input voltage can be 48V, 24V, and 12V. 

The input voltage should be more than the numbers mentioned above for all the higher power output inverters. So, this is yet another rating measure that you will mention on the specification sticker of the inverter. 

Count on it, and you will eventually be able to decide the best size solar inverter for your solar array system. 

Determining the Solar Inverter Size

Layout of Inverter and Panels

Solar inverter sizing varies between extensive and trim options. As for the solar panels, the inverter size is also rated in watts. For sizing the solar inverter, the installers will consider three important factors: solar array, geography, and site-specific conditions. 

Here is a brief discussion on how these three factors are taken into prime account for determining the size of solar inverter:

#1 Size of the Solar Array

It is essential because the array sends the DC electricity to the solar inverter. Therefore, the inverter must have sufficient capacity to handle the array’s power that is eventually produced. 

The inverter manufacturer lists the sizing guidelines for the same. They will specify the array to inverter ratio and the capacity that it must have to handle all of the power that the array will produce. You can also check the manufacturer’s details on top of the inverter as industries manufacture it. 

Moreover, this manufacturer information will be mentioned in the product’s specification sheet. The manufacturers will void the warranty if the array size does not match the inverter guidelines. 

It is primarily because there is a possibility that the inverter would malfunction if the array to inverter ratio is not the same as specified by the manufacturers. 

#2 Geography of the Solar Inverter

Geography is also accountable for an essential role in determining solar inverter size. It is because this impacts on complete production of the solar panel system. The properties around different regions have different solar irradiances, impacting power production. 

A single-size solar inverter can produce more power in a particular geographical location with high irradiances than a location with low solar radiation. As a result, two systems of the same type will produce different amounts of DC electricity simultaneously. 

Therefore, the inverters should also have the potential to handle an electrical load of different sizes. 

So, the areas with more sunshine and moderate temperatures should have inverters closely sized to the overall solar panel’s wattage. As a result, it will handle maximum energy output voltage from the array at any given time. 

The panel efficiency will eventually decrease if the solar array goes through low solar radiation or high temperatures. Therefore, the array may produce a low power rating determined under the Standard Testing Conditions. 

A small or undersized inverter can serve the necessary purpose in such scenarios. 

#3 Site Specific Consideration Factors

The design and site-specific factors of the solar array will possibly impact the size of solar inverters. Apart from considering the geography, the azimuth and tilt of the installed solar array will possibly affect the amount of electricity that the system can produce. 

Environmental factors such as dust and shading will play a significant role in enhancing or deteriorating the sun’s rays or sunlight that reach the array. 

The solar installers will account for all of these considerations and equipment efficiencies. And this is important while estimating the complete production of power in a solar panel system. 

These factors will help determine the derating factor of the solar system. Hence, you will use this for determining what it can produce in real-life scenarios. 

The solar panels experiencing more shade are possibly at a more sub-optimal tilt and are facing east. The South region has a higher derating factor. The systems that have higher derating factors will never hit the maximum output. 

If that is the case, a small solar inverter can handle the energy output obtained by the solar array. 

The Concept of Inverter Stacking

String Sizing Setup

If you have a lot of small inverters at your property that you want to stack for more power output, you need to go with the inverter stacking process. 

By adopting this process, you can connect all small inverters and form a big one for better power output. 

If the inverter demands an increase as you have added more solar panels, you can either go for a bigger solar inverter or wire up all the smaller ones together. 

While joining, installing, and wiring two or more inverters, you can generate either voltage or power, producing more than one inverter. 

If two compatible smaller inverters are connected or wired together in series, you can double the output voltage. Hence, this technique is helpful if you only connect two smaller inverters. 

But if you are seeking a parallel connection for doubling your power, the two smaller inverters should pair with a higher power rated solar system as well. 

For instance, if you have wired two 2000 W inverters in parallel, they will potentially handle 4KW of power in total. 

Conclusion

When you correctly match the solar system with that of the solar panels, inverter’s ac power rating, and battery bank, you can eventually improve the overall performance of the grid-connected solar systems. 

You also need to remember that power losses can occur if the inverter is relatively small to operate in specific overload conditions. Therefore, pick an inverter perfectly suitable for your entire solar array setup. 

It will help you out with sufficient power and help you maintain the system for the long term without the need for unwanted repairs and replacement. An inappropriate inverter or solar array within the system might just impose load on one another. Therefore, matching their compatibility is what should be your prime concern.

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