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Is your solar array no longer capable of meeting your energy requirements? Adding solar panels is an obvious solution, but how many of these PV modules can your inverter handle?
A solar array can be up to 130% of the inverter capacity. So if you have a 4000 watt inverter you can install a 5200 watt solar power system. With a 5kw inverter, you can have up to 6.5 kw of solar power.
How to Calculate Inverter Solar Panel Capacity
There are many ways to calculate inverter sizes, but we will stick to the simplest methods. These apply to any solar power system and any inverter setup.
There are two basic formulas:
Inverter watt capacity = solar array size
Inverter watt capacity x 130% = maximum solar panel array size
The first one is straightforward and is what most people use. If you have a 5000 watt inverter, you connect it to a 5000 watt solar array.
The array may consist of any number of solar panels. It doesn’t matter as long as the output is 5000 watts. if you have the Giandel 5000W Inverter this formula will work.
This is the way most people size up their systems. It is convenient and easy to follow. However there are drawbacks to this approach. Mainly it does not account for solar panel energy losses. This is where option #2 comes in.
The second option is called inverter undersizing or overclocking. Overclocking means the system output will be determined by the inverter.
Take the inverter and multiply its capacity by 130%.
With a 3000 watt inverter for example:
3000 x 130% = 3900
With a 6000 watt inverter:
60000 x 130% = 7800
So if you have the SunGoldPower 6000W Max (6 kw) inverter you can install up to 7800 watts (7.8 kw) of solar panel power.
Now you are probably asking, isn’t this dangerous? Won’t the extra power overcharge the inverter?
No it will not. The inverter will reduce the solar power output to a safe level.
Then what is the point of adding more solar panels? The following example shows you how you can benefit from overclocking an inverter.
Overclocking Inverters Explained
Solar panel watt ratings are based on their maximum possible output. But these solar panels incur losses, so they rarely reach full capacity.
A solar panel rated at 250 watts means that is the highest output it can provide. But due to cloudy skies, module efficiency, orientation, shading, sunlight intensity and other factors, the output will be lower, around 230W, 220W or even lower.
Which brings us back to inverter overclocking. If you have a 6000W inverter and a 6000W solar array, how much power does the system actually produce?
Assume the panels are 80% efficient:
6000 x 80% = 4800
The solar array only produces 4800 watts. The inverter is not used to full capacity.
Now suppose you oversize the inverter and install a 7000 watt solar array:
7000 x 80% = 5600
The inverter only loses 400 watts. That is a difference of 800 watts.
If you go with a 7800 watt solar system (the 30% maximum possible):
7800 x 30% = 6240
The solar panels will exceed the 6000 watt inverter limit. The system can trim the 240 watts and you can have the inverter running at full capacity.
And the above numbers assume the panel production are near peak levels. In reality that is only going to be for a couple of hours a day during summer.
In the winter, solar output will be lower and the inverter won’t waste any power at all. With a 7800 watt PV array, the energy wastage will be minimal or nil. This applies to all including 3000 watt inverters running on solar power.
Reminders before Overclocking an Inverter
Before you get too excited to try this, there are some things you need to consider.
Overclocking risks voiding the inverter and solar panel warranty. While most inverters can handle oversizing, not all manufacturers support or recommend this.
If you want to add more solar panels to oversize, they must be compatible with the ones in the array. If you cannot find any compatible PV modules, the only option is to replace your inverter.
That seems a bit extreme, but it makes sense depending on the situation. If the inverter is 6 years or older, it is probably in need of a replacement anyway.
Modern inverters are more efficient so in the long run will save you money. There is also the fact that solar power technology is moving so rapidly that finding panels compatible with older systems can be difficult. If you decide to do this, contact the solar installer. Have them do the installation.
For inverter undersizing / overclocking to work, the solar power output must not be more than 30% of the inverter capacity.
Solar panel oversizing and inverter overclocking are the same. It is always based on the assumption that solar panels incur energy losses and the output can be trimmed if it exceeds the inverter capacity.
What is Inverter String Sizing?
Inverter string size refers to the number of solar panels that can be wired on a single inverter input. A group of solar panels wired in one input is called a panel string. Most string inverters have 3 inputs that can hold 8 panels each for 24 in total.
The specifications will vary so make sure to check the inverter before connecting any solar panel. Generally, an inverter can handle up to 30% more power than its rating. Given that solar panels do not always produce at peak power, this should not be an issue.
The larger the solar array the more effective overclocking can be. But you also have to check the inverter DC voltage input. Temperature is also important as inverters are designed to work under specific temperature ranges.
As long as the inverter runs within its operating range the system will be fine. Inverters with an 8 panel per string limit have a capacity of 5250 watts. This is for each string, so keep that in mind before installing any solar panels.
If you not sure, refer to your inverter and solar panel manuals. All the important specifications are included there so use those as your guide.
Tips For Running an Inverter on Solar Panels
There are several questions that need to be answered. The most important are the following. You may consult the company that installed your solar system for more details.
- How many hours of sun light does your location receive?
- How efficient are your solar panels? What is the average output per hour?
- What is the size of your inverter?
- How much extra power do you need?
- Are you on or off the grid?
- What is your budget?
- How old is your solar power system?
The examples earlier show how much power you can save by overclocking. But the results may be different from yours.
If your area gets a lot of sunlight, undersizing inverters may not be necessary. Otherwise, oversizing your solar panels is a good way to maximize the inverter capacity. If you want to add more PV panels, look for those with at least a 20% efficiency rating.
If you want to replace the inverter, get the largest unit you can afford. Whether you are on or off the grid, it is always better to have more capacity than less. Figuring out an ideal size is easy too. Check your monthly power bill and average your usage. Add at least 10% to the total and you have your inverter size.
Do you have plans of expanding your solar usage? Maybe you are grid tied now but plan to be off the grid in a few years? It might be a good idea to invest in a high capacity inverter today. So if you decide to be energy independent your system will be ready for it.
Once you have decided what inverter and solar panels to buy, it is time for the installation. Unless you are a DIY expert, better let a professional installer handle this to avoid any potential problems.
If you are going to upgrade your solar system, check the other parts as well. We focused on the inverter and solar panels here, but the solar controllers, fuses and wiring might also have to be upgraded if you add more PV modules.