How Efficient Is Solar Energy?

With fossil fuel and natural gas costs on the rise, and environmental concerns more pressing than ever, many people are starting to explore alternative energy sources to power everything including their cars, homes, and businesses. While wind power and hydroelectric power are popular for some applications, solar energy is currently the most popular form of alternative energy for most properties.

Many businesses and property owners are upgrading to solar-powered electrical systems, both as a hedge against rising fuel costs and as a way to make their investments more sustainable. Before making the switch, many property owners want to know, "how efficient is solar energy?" Keep reading to learn everything you'll need to know to make an informed decision on solar panels.

Electrician installing solar panels

What is Solar Energy?

The energy that is produced when radiation from the sun is trapped and converted to usable electricity is known as “solar energy”. Unlike fossil fuels, there will never be a shortage of solar energy, and minimal effort is required to harvest it. Harnessing solar energy is a fairly straightforward premise – all you need is an array of solar panels to trap and convert the sun’s rays and solar batteries to store the energy once it’s created.

Here’s a little more information on how this process works.

How do Solar Panels Work?

Solar panels are collections of solar cells which convert light into electricity. Solar cells are made of semiconductor materials which begin to lose electrons as they are heated by the sun. These lost electrons are then channeled through the cell, which becomes electricity.

Small solar cells spread over an expansive area can work together to provide enough energy for the system to sufficiently power homes and businesses. The more light that hits a solar cell, the more electricity it can produce.

Types of Solar Panels

There are three main types of solar panels that can power buildings. Monocrystalline, polycrystalline, and thin-film all are capable of converting light to electricity, each providing its own set of benefits.


Monocrystalline panels are made of an individual pure silicon crystal from a singular source. They are cylinder-shaped, uniform in color, durable and long-lasting, and capable of generating between 300 and 400+ watts each.

The image you may have in your mind of a typical solar panel is most likely the monocrystalline type. The reason for this is simple, and that’s because monocrystalline panels are among the most commonly used.

All solar panels offer some level of energy efficiency, but with up to 20% efficiency, monocrystalline panels are considered the most efficient. This rating means that 20% of the sunshine that hits a monocrystalline panel is converted into usable energy.

Because they are more expensive to produce, monocrystalline panels often require a more considerable upfront investment than other panels.


Polycrystalline panels are made from many different pieces of fragmented silicon that are melted together and may come from other sources. This manufacturing process is less expensive than making panels out of monocrystalline panels and their individually sourced silicon crystals.

However, polycrystalline panels can be less efficient than monocrystalline panels, producing around 250 watts of power each rather than 300 or more. They also tend to have a lower efficiency rating, typically in the 13-16% range. Aesthetically, though, they strongly resemble their monocrystalline counterparts and can last almost as long.


Compared to monocrystalline and polycrystalline solar panels, thin-film panels are comparatively lightweight. Their structure is malleable, while the others are rigid, making them easier to install than the thicker, heavier varieties. Thin-film panels are also less expensive to manufacture than other solar panels and are more affordable to install.

Unlike monocrystalline or polycrystalline panels, thin-film solar panels can be made using three different materials: Amorphous Silicon (a-Si), Cadmium Telluride (CdTe), and Copper gallium indium diselenide (CIGS).

Amorphous solar panels are silicon-based, like mono and polycrystalline panels, but the silicon portion is only the first of three very thin layers. Amorphous panels can withstand intense heat and are more adept at generating energy on darker days.

Cadmium telluride (CdTe) panels use cadmium telluride in a thin semiconductor layer designed to absorb and convert sunlight into electricity. Cadmium telluride PV is the only thin-film technology that costs less than conventional solar cells, but there is some concern about the toxicity of cadmium. Because of its toxicity, the mining of cadmium creates environmental concerns.

Copper gallium indium diselenide (CIGS) thin-film panels, on the other hand, are extremely expensive to produce. These cells have copper, indium, gallium, and selenide layers on top of each other. Toxic materials are also used to create this type of thin-film panel, making them a less sought-after option.

Depending on the material used, thin-film solar panels have an efficiency range of 7-18%. A lower efficiency option would require more panels to generate the same energy amount as a higher efficiency option, ultimately costing more out of pocket.

What are Building Integrated Photovoltaic Panels?

Building-integrated photovoltaics (BIPV) are different from traditional solar panels in how they are attached. While traditional panels are usually attached to the building, building-integrated panels are built directly into the rooftop’s materials.

This makes BIPVs dual-purpose: they are both the outer layer of a given structure and generate electricity for on-site use, with any surplus capable of being exported to the grid. Because of their “two birds, one stone” nature, BIPV systems may help you save on materials, see a reduction in your electricity costs, and reduce your carbon footprint.

It is possible to retrofit a building with Building Integrated Photovoltaic Panels; however, their most significant value is achieved by including them in the structure during initial construction. The substitution of BIPV for standard construction materials can eliminate costs and design issues for separate mounting systems that would be necessary to add solar panels to a building.

BIPVs can be made out of any of the crystalline solar cells or thin-film technologies.

Just How Efficient is Solar Energy?

Solar efficiency is determined by the type of solar panel installed or integrated into your building. Panels with a higher energy conversion will provide a higher energy efficiency than those with a lower energy conversion rate. While advances in technology and materials have made solar panels significantly more efficient over the years, some people are still unsure if current efficiency levels are adequate for their homes. Here’s how it works.

Solar Energy Efficiency

Solar panel efficiency is measured as the solar panel’s ability to convert sunlight into usable electricity.

For example, if the sun shines on a solar panel with a 20% rating, 20% of the sun’s energy will be converted into electricity.

Suppose the same amount of sunlight shines on two solar panels with different efficiency ratings for the same amount of time. In that case, the more efficient panel will produce more electricity than the less efficient panel.

Most commercial solar panels have an energy efficiency rating between 11-15%; however, some residential panels have an efficiency rating of up to 20%.

Cell Efficiency

Solar cell efficiency determines the solar panel’s efficiency, which is influenced by composition, electrical configuration, surrounding components, and more.

Panel Efficiency

These days, most solar panels have between 15-20% efficiency. High-efficiency panels can exceed 22% efficiency, but most commercially available photovoltaic panels have no more than 20% efficiency.

Are Solar Panels 100% Efficient?

No type of energy is 100% efficient. Some energy is always lost as heat during the conversion process. Because conditions for solar panels are never perfect, they will never be 100% efficient.

There are quality accessories that are compatible with solar panels to help ensure that you don’t lose excessive amounts of energy.

How is Solar Panel Efficiency Calculated?

The efficiency of a solar panel is determined by comparing the sunlight that falls on the panel to the amount of electricity it produces. If a panel could convert all of the light that falls on it into electricity, that panel would be 100% efficient. Unfortunately, this level of efficiency is impossible.

A simple formula makes calculating your panel’s solar efficiency easy. You’ll need to divide the maximum power output by the panel’s total area in square meters. Then you will multiply that number by 100 to get a percentage. The maximum power output should be in Watts and is usually located on the module’s datasheet.

Factors That Impact Solar Efficiency

Unfortunately, solar energy doesn’t provide 100% efficiency ratings. Several factors impact the solar efficiency a building can achieve, with some having a higher impact than others. Some of those factors include:

Outside Temperature

Because solar cells work optimally under specific temperatures, solar panel efficiency can vary with fluctuations in temperature. There’s a misconception that higher temperatures can increase solar panels’ efficiency, but higher temperatures are negatively correlated to solar panel performance. Higher temperatures can also damage and even negatively affect the performance of your system.

Solar panels perform optimally between 59°F and 95°F. Their efficiency starts to drop a portion of a percent for every degree above 95°F, typically .2%-.3% per degree.

Extreme Weather Conditions

Extreme weather conditions can also impact the performance of solar panels. Because solar cells work optimally under specific temperatures, any severe weather can have an impact on their efficiency.

For example, if a snowstorm buries a system and completely prevents sunlight from reaching the panels, the solar efficiency will be 0%. However, in the case of snow, because it is bright and highly reflective, a quality known as irradiance, as long as the panels aren’t buried, snow can actually increase the amount of light that reaches a system.

Thermal Cycling

Thermal Cycling, or Temperature Cycle testing, is performed on solar panels to determine their resilience in the face of exposure to alternating extremes of high and low temperatures. Thermal mismatch of materials, meaning the materials used respond differently to the same temperatures, can cause cracking of soldering and joints, warping, and hermetic seal failures.

Dust and Grime Build Up

This seems like a no-brainer, but the output power of a clean solar module is at least 5% higher than that of a dusty module exposed to the same conditions. The more dust and grime on the module, the greater the decrease in the output performance will be.

Dust and grime can accumulate on the surface of solar panels and block light from reaching the cells, reducing their potential to generate power. The amount of energy lost due to soiling is highly variable, depending on the dust and its accumulation level.

Solar Panel Color

The majority of solar panels are a dark blue or black color. Monocrystalline solar cells are primarily black, gray, or blue, and polycrystalline solar cells are almost always blue. Darker coloration absorbs as much light as possible, making them more efficient than their lighter-colored counterparts.

Solar Panel Orientation

The ideal orientation of your solar panels will, of course, be where they get the most sun. In most cases, this placement will be the part of the roof with southern exposure. However, based on your building’s design and the shading of your property, it might not be ideal to put your panels facing south. Shading due to trees, buildings, terrain, and other environmental objects, obstructs irradiance and will impact your solar panel’s energy absorbance.

Inverter Efficiency

Converting your DC energy into AC via an inverter typically generates around 96-97% energy efficiency. Inverters typically have higher efficiency when the DC input power is high. The conversion efficiency takes a big hit when the input power is much less than the inverter’s rated power.

Get A No-Obligation Solar Panel Installation Quote Today

Upgrading your property to utilize solar energy is a great way to reduce or eliminate your monthly energy costs and drastically reduce your carbon footprint. Suncoast Power has specialized in commercial and industrial power installations and upgrades, including solar and other alternative energies, for more than 30 years.

Call Suncoast Power today at (754) 200-5872 or fill out our online contact form to speak with a team member about your energy requirements. Our representatives are standing by to answer any questions you may have and schedule an initial site visit.