Ground-mounted solar panels: Which mounting system is best – single-pile or double-pile?

There are two main types of mounting systems for ground-mounted solar panels: single pile and double pile.

• In single pile systems (Single Post), each row of panels is supported by a vertical pile at each support point, on which the rack carrying the panels is placed. This is a simpler and more flexible construction that is gaining ground in areas with stable subsoil.

• In double pile systems (Double Post), each support point includes two piles that work as a pair, offering increased stability. The beams – horizontal and diagonal – reinforce the structure and make it ideal for unstable soils and areas with severe weather conditions.

The choice between the two depends on many technical, economic, and geotechnical parameters, which we analyze below.

Technical evaluation is the first and most important factor in choosing a base. Below we present the basic differences in detail:

The single pile system offers satisfactory static stability, provided that a proper geotechnical study has been carried out beforehand and the pile driving is sufficient in depth and diameter. However, because all loads are transferred to a single pile per point, it is more sensitive to headwinds if the necessary measures are not taken.

The double pile system clearly excels in terms of stability. The distribution of loads across two points reduces local stresses, while the reinforcements improve the behavior of the structure under seismic stresses and extreme weather conditions. It also offers increased safety in soils with varying bearing capacities.

The choice of support base is directly related to the type of subsoil. In stable and cohesive soils, such as clayey or rocky, the single pile system can provide satisfactory support with deep pile driving. However, to achieve the required stability, the pile must penetrate to a sufficient depth, which increases the requirements in terms of length and material quality.

In contrast, in unstable or loose soils – such as loose fill or areas with groundwater – the double pile system is superior. It distributes the loads to two support points, offering greater resistance to settlement and lateral displacement, while the piles do not need to reach such a great depth, partially reducing the technical difficulty of pile driving.

Single piles have an advantage when it comes to installation on sloping ground. The smaller number of piles makes it easier to align the rows without the need for absolute parallelism. In contrast, with double piles, because the piles work in pairs, more precise alignment is required and more time is needed on site for adjustments.

Single-pile systems require fewer materials, as the beams are lighter, fewer piles are needed, and the total amount of steel per MWp is lower. In contrast, double-leg systems have more components, larger hypotenuses, and often require welding or additional anchoring mechanisms, increasing installation time and overall complexity.

In terms of flexibility for future repowering, the single-post system allows for easier interventions. The less rigid structure and simpler support allow panel replacement or frame upgrades without major modifications. Double-pole systems are more restrictive in this area due to their fixed geometry.

In addition, monopole systems can support large continuous rows of panels (e.g., 48 or more per table), which facilitate mechanical cleaning and automated maintenance (e.g., with cleaning robots). Double-pole systems often have smaller tables, which can create “blind spots” where manual intervention is required for cleaning or cutting weeds.

Grass cutting in single-row systems can be done by a tractor, whereas in double-row systems, between two rows, it must necessarily be done manually.

The single-pile foundation generally has a lower initial cost. Due to the reduced amount of steel and subgrade, the material cost is significantly lower per unit of power. In addition, simpler installation means lower labor and specialized crew requirements, with fewer man-hours and shorter schedules.

However, it should be noted that single-pile support is more sensitive to errors during pile driving. If the pile is not of sufficient depth or is not installed correctly, problems with static instability or skewing may arise.

With double piles, increased material consumption and more work on site raise costs – typically 10–20% higher per MWp. However, this additional cost can be offset in the long term by reduced risk of structural failure or repair needs.

Another factor is the utilization of the available space. Single-pole systems allow for a denser row layout, with narrower aisles (up to 2.5 meters) – something that is particularly useful when space is limited or when bifacial panels are used that benefit from reflected light. If space is even more limited, the solution is 2V double-row systems, which produce more power per square meter. If space is extremely limited, we can opt for 3V double-row systems with a low slope of 10-15 degrees. Although 3V double-row systems have been successfully implemented in other countries, they are not suitable for Greece.

There is no one “right” answer for everyone. The choice of solar mounting system should be based on technical studies, financial calculations, and strategic thinking about the sustainability of your project.

If you want a flexible and cost-effective system, especially on good-quality soil, then single-post mounting is an excellent solution.

If you want a flexible and cost-effective system, especially on good quality soil, then a single-post base is an excellent solution. On the other hand, if your project is to be developed on demanding soil or in areas with extreme weather conditions, the double-post base will offer increased stability and long-term security.

At Axinar , we know that every photovoltaic project has its own needs. That’s why we’re here to guide you in choosing the right support system, based on quality, efficiency, and safety.