Solar Panel Energy Efficiency

Energy efficiency is how much work or power it takes for something to produce energy. Therefore, the less it takes to generate energy, the more efficient it is. A more energy-efficient solar panel uses less energy to achieve the same output as a less efficient one. This is a significant factor to look out for because increased energy efficiency lowers greenhouse gas emissions and electricity bills.

Efficiency Rating:

Solar panels have become increasingly more cost-efficient due to their improvement in overall efficiency, increasing from an average 15% efficiency rate to an average 20% efficiency rating. Although a more efficient solar panel may have a higher upfront cost, it will result in more savings because there is less energy waste. The efficiency rating of a solar panel is how much of the sun’s rays are converted into energy versus how much energy is lost or wasted. The ratings- 20.6% – 22.8% are very efficient solar panels, with the highest efficiency recorded at 24.5% commercially.

Power Rating:

The power rating of solar panels has also increased in recent years. This means how many watts it can generate. Residential solar today generates around 350-400 W. However, the actual wattage that a solar panel produces can depend on external factors like sunlight, trees, and seasons. This is what makes the productivity of solar panels higher in sunny months like July and lower in cloudy months like December.
External factors that can affect solar panel efficiency:

• The amount of light reflected away from the cell’s surface.
• The intensity of the sun
• The amount of cloud cover
• Tree or building coverage
• Heat build-up affects the conductivity of the semiconductors in the PV cells. This means that as the temperature rises, the less electricity it generates.


The type of material for the panel also affects the efficiency. There are three primary categories of solar panels: monocrystalline, polycrystalline, and thin-film. Monocrystalline panels are the best at making energy and demonstrate the most efficiency. They are photovoltaic cells constructed from a single crystal of high-purity silicon. They have the highest kilowatt-hour output per square foot and are considered the best for residential use.
In contrast, polycrystalline panels exhibit a moderate level of efficiency. Their PV cells are made of multiple pieces of silicon crystals, as opposed to a single piece, making them less efficient. However, the production cost is resulting in a more affordable upfront cost. Thin-film panels are typically the least efficient because they are not made with crystals but a layer of photovoltaic material on a substrate.

 Yet, technological advancements have led to some thin-film achieving efficiency levels comparable to polycrystalline ones.

The Future of Solar:

A recent breakthrough discovered a way to increase solar panel efficiency to 30%. Experts hope to make it commercially available in the next five years. They found that adding another semiconductor layer called perovskite on top of a silicon layer increases energy efficiency. This helps capture more sun rays and increase the total energy absorbed per cell. But to make this high-efficiency solar panel impactful, the installation rate of solar panels needs to increase significantly.

To learn more about solar panels and their efficiency, contact Seed today!

~By Camryn Iftiger, Intern at Seed Solar, Electric and Engineering. Camryn is a 2021 graduate from UVM with degrees in Environmental Studies and English.

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