Guide to help installers detect hidden costs in high-power modules

From pv magazine Spain

A few months ago, in pv magazine, we published a series entitled Light and shade of 500 W-plus solar panels, in which high-power PV modules were analyzed from a technological point of view. Now, the Spanish provider of photovoltaic products Techno Sun has carried out a complete study in which it analyzes the consequences of these large modules for professionals in the sector.

In particular, it has defined how to calculate the additional costs of a high-power solar panel from several points of view, including installation and transport, among others.

The new power ratings in such solar panels entail, at this technological stage, a significant increase in their size that exceeds current standards. In addition, the increase in electrical values ​​means that many inverter manufacturers have to adapt their models or produce new ones. All this represents a qualitative leap that generates consequences for the entire infrastructure currently developed by installers and distributors.

“When we think about the costs associated with solar panels, we have the concept that the larger the panel, the higher the power, and therefore it is more economical,” said Techno Sun. “This idea is erroneous when forgetting other, indirect factors which greatly impact the final purchase and installation price, highlighting that the panels that have the best power/cost ratio are not the larger ones.”

The company also explained that more hidden costs may be found for smaller installations, in particular when the length of the panel exceeds 2.1m. Its experts categorized three predominant sizes of solar panels: ‘Small', with panels less than 1.5m high and featuring 72 cells; ‘medium,' for products around 1.7m high and with 120 cells; and ‘large,' for modules around 2m high and higher (up to 2.4m can already be found) and with a variable number of cells depending on their technology.

How to calculate additional costs

Techno Sun states that it is not only the module purchase price that must be taken into account. “In our experience, there are nine key factors that will greatly affect its value and for which we optimize the portfolio of solar panels for our customers,” the company said. These factors are installation; transport; special machinery; mounting structure; inverter compatibility; power rating and surface; maintenance; replacement; and storage.

Installation

“When installing a solar panel, you have to consider how simple it could be to install and operate it. A large panel with 1x2m size or more, and an approximate weight of 30kg, makes it difficult for a single person to handle, which means at least two people are needed to deal with their handling,” said Techno Sun.

In addition, depending on accessibility to the installation site, it is likely that a third person, or special machinery, will be needed to lift a larger and heavier panel. However, a panel considered medium-sized by Techno Sun, with a height and weight closer to the current standards, can be handled by a single person in a large part of the process. “This implies that in each installation we are saving the costs of an additional worker, with a considerable reduction in final installation costs,” the report notes. 

Transport

Another important factor that must be considered to calculate the cost of a solar panel is its transport, which often goes unnoticed. “From Techno Sun, we warn professionals that transportation is one of the factors that can significantly increase the final price of the products,” it affirmed. It must be taken into account that, if the size of the panel is large, more trips will be necessary to transport all the material necessary to carry out the installation, or a larger vehicle, since it occupies a greater volume of transport.

“For example, if we have a typical installer's van as a reference, with a large panel, there is little space for anything other than the pallet of panels, as no weight can be placed on it to avoid damaging the cells,” the company said. “On the other hand, if it is a medium panel, there would be space for other elements of the installation, such as the inverter, battery, or simply the tools that we are going to use.”

That becomes even clearer if a small truck is taken as a reference. “In this box, we can put up to three pallets of medium panels but it is only possible to fit one of the large panels,” Techno Sun emphasized. “This relationship of three to one can be decisive when calculating the cost of the installation by means of transport and the number of trips to the site.”

Special machinery

Closely related to transport is the use of specialized machinery used both for the loading and unloading of material from the van or truck and for its installation.

“We must bear in mind that the panels of two meters or more come on specialized pallets that are a few centimeters larger,” Techno Sun stated. “For a panel of 2.2m in height, we need pallets of 2.3m long.”

When loading a pallet like this in a van or truck, special machinery will be necessary, since the forks of a mechanical forklift range between 1m and 1.2m. In this way, the panels cannot be loaded horizontally and therefore a conventional forklift cannot be used without the risk of damaging the panels due to the weight in the air or even the pallet falling to the ground. As a consequence, a deep forklift is needed, which results in additional cost in machinery.

In small installations, where the panels have to be raised to roofs or terraces, the smaller products can be transported by a single person, both by stairs or elevators, but in the case of larger ones, special machinery is necessary to be able to upload them to the installation sites, with the large increase in price that this may entail.

Mounting structure

The fourth factor is related to the mounting structure used in a PV system. The size of the mounting system is determined by the size of the modules, which means holding a panel measuring 1m and weighing 27kg is not the same as holding one longer than 2m, and of around 30kg.

In current structures, the panels are fastened with two rails and four lateral anchoring points. This is sufficient for a medium-size module as it ensures a good grip, and that the panel will not suffer from movement or twisting when the wind exerts forces on the front and rear sides of the panel. However, in the case of larger panels, if the solar panels are to avoid possible damage and ensure proper operation, they should be installed with three rails instead of two, with an additional rail placed in the center, and with six anchor points to ensure them the stability they need.

Therefore, if a solar panel is installed properly, the costs will be higher, as there are a greater amount of structures to place, with the corresponding increase in time and money invested in materials. If, on the other hand, the installer risks installing a high-power product as if it was a smaller panel, the risk of malfunction or damage increases, resulting in increased costs due to poor installation that impairs the durability of the product.

Inverter compatibility

When choosing an inverter for a solar array, it is necessary to consider that the higher the power of the panels, the fewer inverters will be compatible with them, leading to having to choose large-capacity inverters to install products of more than 500 W.

This is due to the relationship between the maximum output current of the solar panel and the maximum input current of the inverter. Solar panels over 505 W have a maximum output current that can reach above 17 A, while panels between 480 W and 505 W range between 11.5 A and 12 A; modules between 430 W and 480 W are among 10.5 A and 11 A for maximum output current; and those under 430 W are below 10 A.

This means that more than 40% of the inverters on the market are not prepared for panels of more than 505 W and those that are compatible are usually for large scale installations. In turn, around 30% of the inverters on the market do not support panels of more than 450 W.

“Retrofitting installations with higher-power panels will result in the need to also replace the inverter,” Techno Sun highlighted.” At the same time, costs will increase in new installations with high-power panels as installers have to opt for a larger and more expensive inverter with the capacity to withstand their maximum current.”

Power rating and surface

The common belief is that the larger the size, the greater the power output from an installation, but this assumption is not entirely true, as one of the key factors is space and surface.

Although a large panel has more power than a medium one, the size versatility of the second can allow more panels to be deployed. For every two medium panels, there will only be space for one large one; for three of the first only two of the second; for four, three; for five of one, four of the other; and for six small, only four of the large ones.

That means being able to install more power on the same surface by using smaller panels, in addition to the other advantages that this may entail in possible maintenance and replacements.

Maintenance

Whether a panel needs maintenance or repair, its size is a determining factor for cost.

“The repair and maintenance of larger panels are more complicated, due to the difficulty of handling them, so, as with the installation, it is likely that more personnel will be needed, and therefore more labor costs,” the company said. “We will also lose more total power in the installation if a large panel with more power than a medium one breaks down.”

Replacement

If it is necessary to replace one solar panel with another, it will be more expensive for the customer to replace a larger and more powerful one than a smaller one. This operation may also include the change of mounting systems. Their cost is higher because the cost of the product itself is higher, as well as its installation and transport.

Storage

As with transport, the larger the size, the higher the storage costs. This logistical detail can be crucial as it is not the same to be able to store two pallets in the same place as one.

For a professional, having less stock implies that it will be necessary to place a greater number of orders as stocks are consumed and the greater the number of orders, the higher the costs associated with them.

Conclusions

According to Techno Sun, if an installer is looking for the best final ratio between power and price, opting for medium panels, rather than large panels, should be considered the best option. “Thanks to the cost savings derived from the smaller size, the cost per panel throughout the entire supply and installation chain will be lower and, cumulatively, there will be savings in expenses and a sustainable business margin with the reality of the professional sector,” the company concluded.