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How to define a specific DC capacity for your site

In this article we'll show you how to achieve a specific DC Peak Power in your plant. This will help you when you need to keep your installed DC power below a certain value.

RatedPower has a function called "Specific Capacity" that allows you to input the AC Rated Power you aim to achieve and identify the required DC power based on DC/AC ratio.

If you need to achieve a specific DC Peak Power you can follow these simple steps.


The "Specific Capacity" option removes a certain number of structures (painted in red in "Preview Map") in order to lower the capacity below the "Maximum Peak Power" value that you can see in the results on the top right of the screen.

If the DC Peak Power you are trying to achieve is above the "Maximum Peak Power" achievable this option won't help you. Try to use a more powerful module, decrease pitch distance, enable partial structures, and select border adaptation to increase the "Maximum Peak Power" and then apply the strategy.


  • Download this Excel file

  • Fill out the inputs (blue cells) with the same parameters used in RatedPower and specify the DC Peak Power you want to achieve.
  • The file will tell you if the desired DC power is exactly achievable or not. In the former case, you'll see the parameters to use to achieve that specific power, in the latter, you'll see the two closest options (DC power slightly below and above the target)

The DC Peak Power is obtained by multiplying the DC power of a PV module by the total number of modules in your plant. Since modules are grouped in strings and strings are installed in structures, the total DC Peak Power can't vary continuously but only in a discrete way by adding or removing structures. A specific value might not be achievable because it's not a multiple of the DC power of the shortest structure.

  • Let's take a closer look at the results.
    • In the first line, you have the DC Peak Power that will help you to decide which option to go for if the exact desired value is not achievable.
    • In the second line, you have different DC/AC ratio options ordered from largest to smallest centered around the "Desired DC/AC ratio" you inputted (if the exact DC/AC ratio is achievable you'll see two identical columns in the center). Select the column with the DC/AC ratio you prefer.
    • Based on the selected DC/AC ratio the Rated AC Power and the relative number of inverters are displayed in the following lines.
  • Input "Number of inverters" and "DC/AC ratio" in the correct field in rated power under "Layout" tab in "Power Requirements"/"Specific Capacity"

For any other questions or more information regarding this topic, you can contact us at: support@ratedpower.com