How Efficient Are Solar Panels?

Harnessing the energy of the sun, solar panels produce green, environmentally friendly energy. But how efficient are solar panels? The answer is determined by several factors: quality and design of the solar cells, physical location of the solar panels (referred to as a solar array), and weather and cloud cover. Atlasta Solar is here to explain how efficient solar panels are as well as help you optimize their efficiency.

What is the Efficiency of A Solar Panel?

Solar panel efficiency refers to the conversion efficiency of photovoltaic (PV) cells. Conversion efficiency is a measure of the amount of sunlight that falls onto a panel and is converted into usable electricity. The first solar panels (invented in the late 19th century) had an efficiency of about 1% only. The first modern solar panels, dating from the mid-20th century, achieved an efficiency of about 6%. Today’s solar panels have an efficiency rate of about 15-20%, with high-efficiency solar panels reaching an efficiency about 23%.

Conversion Rates Increase While PV Panel Costs Decrease

At first glance, these numbers may seem low in terms of energy conversion. However, this is not a major issue, considering that the input of energy (the sun) is free, and that panels are emission-free. It is important to note that the cost of PV panels has dramatically decreased over the years, while solar conversion rates have and will only continue to increase. In fact, every year since 1980, solar panel prices have dropped by at least 10%.

How Efficient Are Solar Panels
Solar conversion efficiency rates continue to increase over time.

Factors That Affect Solar Panel Efficiency

Several factors affect how efficiently a PV panel absorbs sunlight and converts it into usable energy.

Solar Panel Type

The type and amount of solar panels play a critical in solar panel efficiency. Solar panels come in three types, all of which are made of silicon:

Monocrystalline crystalline panels are composed from a single large silicon crystal. Out of the three types these are the most efficient in generating energy, and are therefore the most expensive.

Polycrystalline panels have several small silicon crystals. These panels produce about 1% less power than monocrystalline panels, but are reliable and are the most common type of solar panel.

Amorphous panels have the lowest power yield of the three solar panel types. As a result, amorphous panels require 3 times the roof space of monocrystalline and polycrystalline panels, to reach the same power yield.

Solar Panel Configuration and Design

The configuration or how the panels are laid out is crucial. Atlasta Solar fully evaluates a potential solar system site (for example, such as the amount of sun exposure and roof pitch) to optimize solar system energy output.


Inclination or how the panels are tilted affects conversion efficiency. Also referred to as solar panel angle, the amount of tilt will vary depending on region and time of year. Ideally, solar panel angles should be adjusted each season to optimize exposure to the sun; in reality, this isn’t possible in most situations. It’s far easier to install panels at various angles to accommodate the seasons and roof pitches.


Many people assume that the hotter the weather, the more energy solar panels can generate. Ironically, hotter weather can decrease solar panel efficiency. The semiconductor material in solar panels is sensitive to high temperatures. Solar panels work best in temperatures around 77 F.


Contrary to popular opinion, solar panels do generate energy on cloudy days. It is just that less energy is produced, in comparison to sunny days. Depending on the amount of cloud cover, solar panels produce about 10% to 25% of their usual power capacity.


It’s a simple rule of thumb: the cleaner your solar panels are, the better they can absorb sunlight. Studies have shown that dirt on solar panels can decrease their efficiency by as much as 20%. Fortunately, solar panels are relatively easy to maintain. Their inclination also helps rain and snow rinse off dust and debris.

Do Solar Panels Lose Their Efficiency Over Time?

Solar panels slowly lose their efficiency over time. This is due to wear and tear from the elements. To optimize your solar panels’ lifespan, clean your solar panels when needed. Most panels last about 30 years, with efficiency decreasing by about .5% per year.

How Efficient Are Solar Panels During Different Seasons?

Solar panels only produce electricity when the sun is out. It is important to note that solar panels do generate power on cloudy days, but do not produce as much as on sunny days. Solar panels are most efficient during the summertime, with lowest energy output usually occurring in the winter.

How Efficient Are Solar Panels 2
Solar panels still absorb sunlight and generate energy, even on cloudy days.

How To Optimize Your Solar Panels

Here are several ways to optimize the efficiency of your solar panels:

Clean Your Solar Panels

Have you ever noticed a decrease in your solar system’s energy output? It is possible that grime is obstructing the panels. Clean your solar panels whenever they are dirty. Be sure to review your energy bills before and after cleaning them, so you can see how well the panels operate.

Use A Battery Bank

Did you know that you can store solar energy generated by your solar system? A battery bank allows you to do so. Battery banks for solar systems are typically lithium-ion or lead-ion, and usually, store energy for one to five days.

Have an Expert Install the Panels

To save on costs, some individuals may be tempted to install solar panels on their own. Aside from safety risks (such as falling or electrocution), installing a solar system incorrectly can affect how well they operate. Solar panels are best installed by professionals, as we consider the logistics of a location (weather, temperature, roof angle, etc.), so solar efficiency is optimized. At Atlasta, we ensure that solar systems are properly and safely installed.

Are Solar Panels Worth It?

Some individuals are hesitant to install solar power, given the initial upfront costs. However, it’s worth remembering that having solar power can pay off in the long run and can even increase your home value. Solar systems continue to decrease in price while energy conversion rates continue to increase. For all your solar panel needs, contact Atlasta Solar at 970-248-0057.

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