Solar panels – how to choose the right ones?

More and more people are choosing more sustainable, cheaper solar energy. As this is still a relatively new field, there is often a lack of information about it. For example, Google search for “solar panels” will give you a long list. Many people looking for the best choice of solar panels are probably wondering how to find the most suitable ones and what criteria to take into account when choosing them.

Nikas Savičiauskas, Brand Development Manager at ACC Distribution, has  shared his knowledge.

Let’s start at the very beginning – what criteria should we take into account to choose solar panels?

The most important criteria when choosing solar panels should be: the power of the module, durability, manufacturer’s reliability. The efficiency of the module should also be considered. Solar panels indicate the percentage of efficiency, which ranges from 20% to 22%. The power output of the module itself can vary by 5%, depending on the manufacturer of the solar panel. Typical solar panels are mounted on the roofs of people’s homes and measure 1.1m x 1.7m, so a larger module will save space or allow you to install a more powerful solar power plant.

The panel should also be certified to an international standard to certify that it meets the quality and safety requirements of the European Union. This is because Europe has four specific seasons of weather for which solar panels are adapted. Solar panels for Asian markets sometimes appear on the Lithuanian market and are sold at extremely low prices. They are adapted to dry weather, high temperatures and are less resistant to rain and hail, which makes their use risky. Such solar panels are more likely to fail, have various malfunctions, and have very questionable durability.

Choosing the best or the right panels for your home is not so easy. You need to take into account the energy needs of your home and your budget, the direction and angles of your roof, the capacity, the type of modules. Practically every solar panel project is unique. When the solar panel installer arrives, he or she must assess the entire environment of the occupant and adapt the solar panel to suit, for example, very sunny or often shaded areas. So the best solar panel will be the one that best suits the househald needs and environment.

Nikas Savičiauskas, Brand Development Manager at ACC Distribution

What are the most important technological parameters in solar panels?

The higher the power output of the module, the more electricity the installed solar panel will generate. At the same time, higher efficiency means that more energy will be generated from the sun. Currently, the market is dominated by P-type and N-type TOPCon panels. N-Type technology is not significantly more expensive than P-Type, but over a 20-year period, a solar panel with N-Type technology generates more electricity and loses less of its original features, has lower depreciation, and does not stop generating energy even in cloudy conditions.

The solar panels are connected in a single strand, so if a shadow falls on one of the panels, the power of the whole strand is reduced. Optimisers are integrated to prevent this from happening and help maintain the efficiency of the energy produced. Some new solar panel models already have a partial energy optimisation function.

There are two types of cells used in solar modules, it’s 180 mm and 210 mm. Some manufacturers say that 210 mm cells are the future technology for our solar panels and will dominate, but many manufacturers are still actively producing 180 mm cells.

The evaluation of the manufacturers is carried out by the well-known agency Bloomberg on the basis of its own criteria. Links to the evaluation lists can be found on the internet.

What is the difference between the P-type and N-type technologies you mentioned?

P-type technology is the most commonly used for solar modules and it‘s manufactured using a layer of silicon and boron.  N-type is silicon with phosphor technology. Its production process is slightly more expensive, but this type of module generates more energy and loses less efficiency over time.

It should also be noted that in the first year, the efficiency of a P-type solar panel decreases by about 2% (degradation), then slows down, with an annual decrease of about 0.5%. in comparison, a N-type solar panel loses about 1% of its efficiency in the first year, and then continues to decrease by about 0.4% every year. The timing of the decline in the energy generated by solar panels is always available in the technical specifications of the panels.

When choosing an efficient solar panel for my home, what else should I consider?

Choosing the most suitable panels for your home requires a holistic approach, from your household’s energy needs, to the planned budget for installing the solar power plant, to the direction of the roof, the angles, and the area to be covered by panels.

As for the panel itself, attention should be paid to the design of the module and the solar panel’s cells, which absorb sunlight and convert it into energy, and the glass coating technology. The module’s glass protects the panel and its cells from environmental influences such as hail and the elements, so modules with glass on both sides are more resilient and robust.

There are single-sided modules that collect sunlight from the above, but there are also modules that collect it from both sides, known as two-sided solar modules. The last ones are commonly used in solar parks. On roofs, two-sided generation modules are rarely effective unless the roof covering reflects the light, in other words – covered with non-absorbing material, or additional reflective roof coverings are specially applied to increase efficiency.

Therefore, there is no point in using two sided modules on flat, black, tiled, bituminous roofs as these roof coverings do not reflect sunlight at all.

When choosing solar modules, the environmental shadows cast by surrounding buildings and trees must also be taken into account. Therefore, I highlight once more, it is very important that the professionals responsible for the installation of solar panels take into account the location of the resident’s house, the roof covering and select the most suitable module that will generate the maximum amount of energy in the most efficient way.

When are solar panels most efficient?

The efficiency of a solar panel depends on the technology used in the module, the quality of the installation of the solar panel, as well as the environmental conditions, i.e. whether there are any shadows falling from the surrounding environment, how the modules are oriented (south, east, west), and the angle at which the panels are placed, for example, in Lithuania, the recommended angle is around 35 degrees.

Note the surprising detail that many people don’t expect – solar modules generate less energy at much higher temperatures. Therefore, weather conditions are very important; in Lithuania, solar panels reach their highest efficiency in late spring, i.e. April-May, when the sky is clear and the weather is not too hot.

What is the warranty period for solar panels? How much does it cost to repair them?

Individuals who buy solar panels can expect a warranty period of 15 years or more. Typically, solar panels can last 25-30 years or more without failure, depending on quality, environmental conditions and maintenance.

In general, solar panels are relatively rare and the cost of repair depends on the nature and extent of the fault, the time of the technician, the parts to be replaced and other factors. As I mentioned earlier, the higher the quality of the solar panel, the longer it lasts and the more efficient it is.

What would you say are the biggest mistakes when choosing and maintaining solar panels?

Not assessing site conditions and selecting the wrong capacity solar plant, poor placement of solar panels, not being prepared for environmental shadows. Other mistakes: incorrect installation, poor quality of components, incompatibility with other components.

If I am choosing solar panels for a solar park, what is important to consider?

In such solar parks, it is not the panels that are purchased, but the power they generate, so it is important to pay attention to these technical parameters and to assess the reliability of the owner of the park.

It is also up to the consumer to estimate the annual energy consumption of the home or other property. For example, if a household consumes 1000 kilowatt hours per year, a solar park panel must generate 1 KvW of power, because 1 KvW generates 1000 kilowatt hours per year.

What are the most popular brands of solar panels?

The most popular in Lithuania are Longi, TrinaSolar, Risen, Canadian Solar, Qcel, Jinko, JA solar. Their price range depends on a variety of factors ranging from the power output of the solar panels, to their appearance, to the prevailing price of raw materials at the time of production.

Would you advise me to buy used solar panels?

I would recommend buying new solar panels from trusted manufacturers. Buying second-hand is a bit risky without knowing how long they have been in service, the conditions under which they have been used, how they have been installed and how they have been transported from one place to another. It is likely that used solar panels will no longer achieve the claimed efficiency and may increase the likeliness of a failure.