What Is Solar Panel Efficiency?

Solar panel efficiency is a measure of how well a solar panel converts sunlight into electricity. Today’s residential solar panels are 21% efficient on average (some are up to 23% efficient), meaning that they convert 21% to 23% of the sunlight that hits them into electricity.

Why solar panel efficiency is important

When sunlight shines on your solar panels, only a fraction of it is converted into electricity that your home can use. So solar panels that are more efficient generate more electricity. Does that mean you need the most efficient panels for your home? Not necessarily. The most efficient panels are also the most expensive.

When determining which panels to get, consider these two factors:

1. 
   Space on your roof
   
   . If your roof space is limited and you want to maximize your electricity production, you may want to select more efficient panels. This is especially important if you plan to increase your electricity use in the future by switching to an electric car or an electric heat pump.

2. 
   Lifetime savings
   
   . More efficient panels cost more upfront, but because they generate more electricity, they may save you more over the
   life of your solar system
   . To estimate
   what you’ll save
   over your system’s lifetime, check your solar quotes to see how much your system is expected to produce every year and compare that to your current electric bill. Keep in mind that production figures are estimates, and electricity prices are volatile, so you can only calculate a rough estimate.

Solar panel efficiency is just one factor to consider when
comparing solar quotes
. Also look at your electricity use, proposed system size, cost per watt,
solar inverter
, warranties, and financing options. Choosing a
reputable installer
is key, as they can help you determine which panels will work best for you.

Most efficient solar panels

SunPower solar panels
, the most efficient panels at 22.8%, will cost quite a bit more than any others. You can spend less and get panels rated at 22.2%–22.5% efficiency, which is still high.

The following are the most efficient solar panels, but even less-efficient panels can be very high quality and generate plenty of electricity for your home. You can review your solar quotes to see how efficient your proposed panels will be.

Source:



EnergySage



, a solar and home energy product comparison marketplace founded in 2012.

What affects solar panel efficiency?

The efficiency of your solar panels is affected by factors beyond their rated efficiency, such as these:

• 
  Placement on your roof
  
  . Your solar panels will be most efficient where they get the most sunshine. In the northern hemisphere, that means on a south-facing roof; the second-best positions are east- and west-facing roofs. The installation angle will also affect production; according to the U.S. Department of Energy, the ideal angle for panels on most U.S. homes is between 15 and 40 degrees
  
  
  
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• 
  Sunlight
  
  . The amount of sunshine in your area will affect your solar panel efficiency;
  shading from clouds
  , trees or other buildings can also be a factor.

• 
  Temperature and climate
  
  . You may think solar works best in hot, sunny areas. Although sun is a major factor in solar panel efficiency, solar panels actually generate more energy when they’re a bit cooler. The ideal temperature for solar panels is 25°C (77°F); they will work when it gets hotter, but they won’t be quite as efficient.

• 
  Temperature coefficient
  
  . A solar panel’s temperature coefficient is the amount that its electricity production decreases for every degree above 25°C (77°F). For example, if panels have a coefficient of -0.3, their productivity will decrease by 0.3% for every degree above 25°C. The temperature coefficient of most panels is between -0.3% and -0.5%
  
  
  
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