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How much energy does a solar panel produce?

When you look at a single solar panel, it’s hard to imagine what exactly it is capable of. What can one PV module power and how many do you need for your home? In this article, we’ll dive deep into how much electricity do solar panels produce.

Calculating a solar panel’s energy production

The production of a solar panel depends on two main factors: the module’s rated output and the number of peak sun hours in the area.

A solar panel’s output is measured in watts (W). You might have seen “360W”, “400W”, or “480W” next to the panel’s name. The higher the wattage, the more electricity your panel can generate. Our customers prefer solar panels in the 350 to 450-watt range for home.

Solar panels deliver their promised output during peak sun hours (psh). That’s the time when irradiance reaches 800–1,000 watts per square meter. The number of peak sun hours depends on your location and time of year. The difference in power output of your panels in summer and winter may be up to 40–50%.

Southwest states get more sunlight throughout the year than the Northeast states. For instance, Arizona has 6.30 peak sun hours a day on average, and Michigan has only 4.37. That means that solar panels in Arizona work 2 hours longer and produce more energy than those in Michigan. Check your state in our State Solar Power Ranking.

One solar panel can charge your laptop and keep lights on

Knowing the wattage and peak sun hours, we can calculate how much electricity one solar panel can produce per day:

Wattage x peak sun hours – 25% energy losses from conversion and current transfer = daily power output in kilowatt-hours

Let’s set up an example that is closer to the real world. Imagine that we have a US-made Mission Solar 430W Solar Panel. Say, we’re in Texas with 5.73 sun hours a day. Here’s how much energy this solar panel can produce:

Out of stock

Mission Solar 430W Solar Panel 72 Cell MIN-MSE430SX9Z Assembled in USA

  • Rated Power Output 430 W
  • Voltage (VOC)49.28 V
  • Number of cells72
  • Cell TypeMonocrystalline

Delivery on Jun 25–28

430 W x 5.73 psh – 25% = 1,848 Wh or 1.8 kWh per day

A single 430W solar panel can continuously power several light bulbs and charge a laptop, given that it’s not shaded and the sky is clear. But there are home appliances that require a lot more energy. If you store 1.8 kilowatt-hours from a panel in a battery, you can use it later to cook dinner on an electric stove or do the laundry — no more than that.

30 kWh/day

average consumption of a medium-sized house in America

That’s why to power a house, we need a solar system. To calculate how many panels you need for your house, you first need to figure out your daily consumption. Check your electricity bill and divide it by 30 days. Divide it by the number of peak sun hours in your area and you’ll get the size of a solar system for your home without energy losses taken into account.

Let us do the math

A1SolarStore Calculator helps you figure out the right size of a solar system for your home, choose the panels, and evaluate your savings from solar over the years.

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Considering factors affecting a solar panel’s performance

The rated wattage of a solar panel is determined under Standard Test Conditions (STC). These are reference conditions used by all manufacturers for testing panels. They provide a baseline for assessing the power output and efficiency across the whole solar industry. STC include solar irradiance of 1,000 watts per square meter, a cell temperature of 77 degrees Fahrenheit, and an air mass of 1.5. 

Lab conditions hardly represent the real world with uneven irradiance, clouds, rain and snow. Let’s go over the key factors that may influence a solar panel’s output. 

Overcast skies steal up to 40% of output

Panels don’t like clouds. Depending on the cloud’s thickness, a solar panel’s performance may drop by 20–40% of its maximum capacity. The production doesn’t stop because some radiation still penetrates the cloud cover and lands on panels, even if it’s invisible to the human eye.

Vasilii Smirnov
Solar Installation Expert

Some panels perform on cloudy days better than others. I recommend Canadian Solar or Q CELLS PV modules if you live in a gloomy place. These panels are built to absorb more sunlight in low-light conditions and they bring you more energy in the winter as well.

Wrong positioning may cost up to 30% of production

In America, solar panels perform best when they face south. When your system faces east or west, the average solar panel output per day is 15% lower. When they face north, they produce around 30% less energy.

Solar panels demonstrate the highest efficiency when sunlight strikes them at a 90-degree angle. That’s why the solar panel’s angle should be equal to your latitude or up to 10 degrees less. New York’s latitude is 41 degrees, which means that the panels should be installed at a 45–30 degrees angle facing south.

Shading can kill the production of whole solar array

Shadows cast by trees and neighboring houses are your panel’s worst enemies. Since cells are usually connected in series, even one shaded cell can decrease the production of the whole panel by up to 33% and cause malfunctions. If the entire panel is shaded, energy generation stops completely.

It gets worse if you have a standard string inverter. When panels are connected in series, It lowers the production of every panel in an array down to the level of the worst one. The solution is adding solar optimizers or microinverters.

High temperatures bring production down by 10%

Solar panels prefer cold and sunny weather. When they heat up, their output starts to drop. On hot summer days, their output may decrease by 10% on average. 

The temperature coefficient in the panel’s datasheet tells how much power the panel loses from heat. The temperature coefficient of our Mission Solar panel is -0.347%/°C or -0.192%/°F. It means that each degree above 77°F is about minus 0.192% of the performance.

The problem is solar panels get hotter than the air. The way they are installed, the gap between panels and the roof, the roofing material — all this affects how hot solar panels get. You read more about how much energy do solar panels produce on hot days in our article about temperature coefficient of solar panels.

Years of experience in translation and a love of nature help Julia find the right words to encourage going solar. She joined the team in 2023 and is happy to make her contribution to a greener future.

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