Calculate solar mission wiring wants upfront for probably the most correct BOM estimates


With PVcomplete, users can determine conductor needs based on module and inverter type.

By Olivia McShea, Head of Sales and Marketing at PVComplete

It is not uncommon for a bill of materials to serve as an essential economic data point in early-stage solar projects. The problem is that with BOS (Balance of System) costs, most preliminary BOMs only include shelves and inverters, and not those Cables / wires and other components that make up the BOS. Given that the cost of cabling is very high, calculating cabling needs in advance is essential to develop a more accurate and informed analysis of the total project cost.

Although some project developers have developed their own Excel tools to calculate wiring needs, they require a cumbersome manual process that makes it difficult to compare different project scenarios. They are seldom used in the early stage assessment and are instead only taken into account at the end of project planning.

Fortunately, new advances in solar design software are automating bill of materials calculation and giving developers better insight. With the option of considering BOS accessories at the beginning, developers can for the first time include the entire BOS in the project costs.

By simply selecting the module type and inverter, software algorithms can perform behind-the-scenes calculations to determine the optimal length and size of conductors according to NEC code standards, and based on the specified conductors what size line is required.

Roof applications

Take a look at this representative roof mounting project. The layout includes a certain brand of single-phase inverters mounted on the roof near the main maintenance panel. Sophisticated solar design software offers the ability to optimally place all conductors, draw them on the layout and label them as conductor 1, conductor 2, etc. If desired, users can fine-tune the automatically placed conductor direction or paths to indicate the route they want.

The real computing power is shown in the layout comparison. What happens if you move the inverter to the other side of the building – maybe on the ground floor? Within minutes, the software shows how the cabling requirements change depending on the location of the inverter. Since advanced solar design software is informed by important inputs such as the roof height, the cabling calculations for roof-floor runs are also more precise.

The result is a BOS that is sufficiently detailed to calculate exact project costs and simplify installation comparison.

Floor mounting applications

In our example for a commercial building, a three-phase ground inverter is required. In this case, the position of the inverter on the property has a significant influence on the length of the cable runs.

The advanced solar design software makes it easy to compare the cabling requirements associated with positioning the inverter in the array location and running AC power cables to the main service panel at the connection point with positioning the inverter near the connection point, DC wires back to the array would be required where trenches and operations take place.

With a BOS-informed early-stage parts list, project developers can remove guesswork from the equation from day one and create a more accurate and bankable cost analysis. Advanced solar design software makes it possible.

Olivia McShea oversees PVComplete’s sales and marketing activities. As the main contact for PVComplete customers, she supports solar companies with entry, training and further support. She also supports companies in their search for customized software solutions via PVComplete. In addition, Olivia acts as a liaison for design services in the residential, commercial and utility sectors. Olivia leads marketing strategy and execution to maintain and build relationships across the solar industry. She previously worked in solar distribution helping installers develop and source materials. Olivia studied Climate & Energy at Princeton University and enjoys rowing in her spare time.

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