What Factors Determine Solar Panel Efficiency?

The word efficiency comes out a lot when you’re looking for solar panels. So, you must be wondering how efficiency can be measured and what factors determine the efficiency of your solar panel?

Not all panels have the same built, its efficiency ratings, power ratings, and degradation rates set them apart from one another. Higher efficiency doesn’t make a system better, it just means that your solar panel can generate more energy even in a small area.

All of the sunlight that reaches your PV cell is not converted into electricity. Most of it gets lost because of various factors in solar cell design. The construction and design of a system can limit a cell’s ability to convert the amount of sunlight it receives.

How to Achieve Higher Efficiency from Solar Panels?

These are some of the factors you must keep in mind to increase the efficiency of your panel.

  • Wavelength

Light is a composition of photons with a wide range of wavelengths and energies. When this light strikes the surface of your solar cells, some of its photons are reflected back and others pass right through.

The energy of the absorbed photons is turned into heat whereas the rest offers just the right amount of energy, separating electrons from their atomic bonds. This can produce charge carriers and electric current.

  • Recombination

It is one of the main factors that limit efficiency. Direct recombination is when the light-generated electrons and holes encounter each other and recombine to emit a photon. It reverses the process and generates electricity in a solar cell.

Indirect recombination is when the electrons encounter some defect in the crystal structure, an impurity, or an interface that allows it to recombine and release the energy as heat.

  • Temperature

Higher temperatures can cause the semiconductor properties of the panel to shift. This results in a decrease in voltage and a slight increase in current. An extreme increase in temperature can even damage the solar cell along with other module materials that will leave you with shorter operating lifetimes. Proper thermal management can improve both efficiency and lifetime.

  • Shade

Anything that blocks your panels from getting all the sunlight is an enemy. If you have trees or roof obstructions, you need to remove them in order to gain optimal usage out of your system.

Scientific Factors that Affect the Efficiency of Solar Panels

There are two major components that impact the efficiency of solar panels:

  • Reflectance Efficiency

It determines how much sunlight is reflected back instead of being absorbed and put to use. Lesser the reflection, the better the solar cells. Silicon reflectance is about 38 percent but with a slight micro-pyramid shape, it reduces down to 11 percent.

In order to reduce reflectance, you can either use anti-reflective coatings or stack micro/nano-sized arrays right on top of larger structures.

  • Thermodynamic Efficiency

It is the maximum possible efficiency of the system. It is the level at which solar energy can be converted into electricity. The photons interact with solar cells and generate electricity only up to a certain point. After about 86 percent, the thermodynamic efficiency limit is reached and heat is created.

In order to improve thermodynamic efficiency, you can construct multi-junction tandem solar cells. It helps to improve efficiency by dividing the solar spectrum into small areas, raising the efficiency limit in each section.

The Importance of Solar Panel Efficiency

The panels with a conversion rate of 8% require twice as much area than solar panels with rates of 16%. This is a reason why most homeowners opt for monocrystalline panels that offer higher efficiency ratings.

FAQs on Factors that Determine Solar Panel Efficiency

Yes, latitude has a major impact on solar system production. Generally, a system mounted at a higher latitude yields lower production numbers throughout the year, because of the tilt of the earth spinning on its axis.

A resident of the northeastern US will need to install a larger system than a homeowner in the southwest location to offset their power consumption bill. If your system’s performance is affected by the latitude, there is not much you can do except consider relocating.

Yes, the change in climate conditions can have a major impact on your solar system’s performance. The most common myth is that the module produces less energy in cold temperatures. Heat is the actual enemy, as overheating will reduce the efficiency of your system.

Furthermore, snow can help to improve the overall irradiance as it is reflective and concentrates sunlight. So your system will benefit from the cold environment as long as nothing buries your modules.

The tilt of your solar panels needs to be adjusted throughout the year as the sun is lower in the winter but higher in the summer. The system designed to track the sun is more expensive and requires heavy maintenance because it has moving parts.

Every fixed-tilt system comes with an optimal angle in which it can make the most out of each season. It might not make a drastic difference in a year but the difference over a lifetime of your system can be substantial.

Where you install your modules can make a difference in its production. The best option is to position your modules in a south-facing direction. The second best option is west and the third option being east.

Most solar panels are 15 to 20 percent efficient. However, high-quality solar panels can go up to 22 percent efficiency, but the majority of photovoltaic panels do not go above 20% efficiency.


The efficiency of any solar panel can be impeded by environmental factors. But with proper design and construction, some of these factors can be mitigated. Efficiencies are obtained by measuring the current and voltage produced for various load resistances with proper exposure of the cell to a constant, standard source of light and constant cell temperature. If you have enough roof space, you can get a less efficient but more cost-effective panel.