# Why do solar panels have a peak power?

Written By: | Last Updated On: August 6, 2022

Every solar panel system comes with a data sheet that can be confusing to some to understand at first.

One of the most important terms is peak power or kWp. What does it mean and does it matter, that’s what we are going to talk about in this article to make everything clear.

Peak power in solar panels (kWp) is the highest amount of energy that the system can produce theoretically. Every solar system produced must have specs to deal with it.

And peak power is one of these specs that we need to know to get the best performance. We can compare peak power in solar panels to horsepower in cars for more understanding.

## How to determine the peak power of solar panels?

In the process of producing solar panels, they go through several tests and measurements.

One of these tests is the power output of the panel, also known as standard test conditions.

This test is made under very specific requirements and conditions. The main idea to get the peak power is to measure the current and voltage of the solar panels while changing the resistance under specific illumination.

In this test, the solar panel is tested like it was in the real world or in a normal day. The test is done at an ambient temperature of 25ْC and a standard airmass of 1.5 with a spectrum similar to sunlight hitting the earth’s surface at latitude of 35N in the summer.

All these conditions simulate the conditions that the solar panel will encounter on a normal day in the real world.

## What does kWh mean?

kWh stands for kilowatt-hours, which is the amount of energy your system produces every hour.

On the datasheet that comes with the solar system, there is a term that is regularly repeated. That term is kW or kWh.

Watt is a unit of energy that represents the power output of a system. kWh means the amount of energy produced in one hour. For example, a 4 kWp solar system would have an output of 4 kW after one hour in ideal conditions.

## What are the conditions that affect the solar panels’ peak power?

A solar panel doesn’t have a constant power peak as the output changes constantly. This happens due to many factors that happen every day in the world. For example, any change in temperature, amount of rain, or even passing cloud can affect the output of the solar system. That’s of course before even taking in consideration the geographical location, weather, orientation or panel test.

Let’s take temperature for example, on high temperature days the resistance causes the voltage to fall as heat increases the resistance in the solar panel. The studies also have shown that the cooler the weather is the better is for the solar panel output. That’s why the best output of solar systems is between March and May on a sunny cooler day.

### Roof panels

In roof panels, there is more ventilation due to the wide area which helps in decreasing the temperature. The direct exposure to the sun also helps in absorbing the most amount of light possible. That’s another example of how that factors can affect the solar system performance.

In conclusion, solar system output can be affected by many factors. We can control some of these factors to get the best performance and output and some we can’t.

## The importance of peak power performance in solar panels

After all we had talked about, you start wondering, does peak power really matter?. The answer of this question is divided into 2 pieces.

The first part is that no, it’s important to study peak power in labs and know its effects but it’s not something you worry about when installing the solar system.

The second part is yes, peak power is a very important factor to study the performance of the solar system through the year. This is one of the most important things to keep in mind. Is the system developing or does it need maintenance or other factors?

So focusing on observing the change in the generation of the system daily and annually is a really important matter that deserves your attention.

Lastly, to conclude what we have said, when you are looking at the datasheet of the solar panel, the bigger the number is of the peak power the better the performance of the solar system.