What is it that solar PV designers do? What are their responsibilities and what’s required of them?

First, it’s important to note that there is are geographical differences between solar PV designer responsibilities. In the Northeast quadrant of the United States, the designer and project manager have separate roles. However, many companies in the Colorado area combine these roles into a “project engineer.” Thus, one project engineer will follow a job from the beginning to completion and handle all of the site visits, paperwork, design work, and labor management. For the sake of this article, we’ll be writing from the Northeast perspective.

One unique thing about companies specializing in solar is this: they understand incentives  and how to design systems very well. They tend to have sales forces too, and more and more of them (in Massachusetts, anyway) are subbing out the specialized engineering and installation labor completely while keeping their own project managers. Smaller companies tend to do the installation internally but also tend to work on smaller jobs so the labor is less variable.

The design team is one critical element to every company, so most of them do it in-house. On the flip side, one design engineer can support a large number of projects. It’s also a critical aspect to the success of a company — bad design can waste time and money and produce suboptimal systems.

Performing high quality and efficient site visits is absolutely critical to the success of profitable and well designed solar projects, especially residential projects! During these visits, you need to be able to capture all of the information you need to

  1. Quote the system correctly
  2. Design the project
  3. Inform the installation crew what to expect.

An efficient site visit process will lead to smooth operations and profitable jobs, while a messy or complicated visit can lead to confusion and subpar work.

With that in mind, here is an overview of what a good designer needs to know…

Production Modeling

Now that the industry is growing and systems are getting larger and larger, production modeling, (specifically comparing the performance and cost of different layouts and pieces of equipment) is critical. Why? Because the customer wants to get the most production for the least cost on their roof and investors need to make sure that the systems will create the power that was estimated (as financial returns are often based on production amounts.) For this reason, many property owners will hire an engineer to double check the designer’s work. Today, a plethora of software exist for production modeling.

Engineering Background

Most large companies like to hire workers with engineering backgrounds. In reality, this is not absolutely needed to learn the skills. I’ve seen plenty of self-taught designers, and even people who majored in philosophy, learn how to design a system. Here’s the key: if you have an engineering background, it’ll be easier for you to get into a large company. If you do not, and need to learn and cultivate your skills, so focus on the smaller companies.

The reality is that you can side-step your way into any industry through a relationship.

Electric Code

Designers need to be very familiar with code, as these individuals are typically responsible for creating the three line diagrams and evaluating open circuit voltage, as well as formulating others array layout calculations that the inspector or engineer will be double checking.

Structural Engineering

Solar designers never perform structural work, though they do need to be familiar it, because the decisions they make regarding modules, racking and fastening mechanisms, will affect the structural loads on the building. The system designer will need to be familiar with the terms and processes of the structural engineers and what documentation is needed to pull the building permit in a specific area. They will be communicating with the engineer regularly. Typically, the structural engineer is one of the first people sent out to asses a building (always on a commercial site but very rarely on a residential site), because most commonly, the structural integrity of the building is one of the few things that will stop a solar project. Electrical issues are easier to overcome.

Racking and Balance of Systems

Though designers do not need to be experts on racking, they need to be familiar with it. In the vast majority of cases, designers will send their array layouts to the racking company, who will then create a racking structure for them. The racking manufacturers will need to be in contact with the structural engineers for loading issues — depending on if the system will be fastened or ballasted to the roof.


Typically the solar designers themselves will only be responsible for the design up to the inverter, covering all of the DC loading. They will pass the designs on to an electrical engineer for the AC wiring to the point of interconnection. This is especially true for larger systems.

Sizing Equipment

Designers must be adept at selecting and sizing equipment for different circumstances. Thus, they must be well-versed in inverter and module terminology, and which function best in different situations. Designers should know modules, combiner boxers, disconnects and inverters and need to be familiar with wiring type and sizing, as well.

String Sizing

Part of the designer’s main job will be string sizing. This is done to ensure that the modules produce enough volts to turn on the inverter. They also need to make sure the modules will never produce enough volts to break the inverter.

Wire Sizing

After the strings have been sized, the designer is also responsible for sizing the wire. The size of the wire will depend on site-specific characteristics, such as how long the runs are, and also the company’s accepted tolerance for voltage drop. Wire sizing is incredibly important because under-sizing wire can lead to overheating and, in some cases, fire.

Module Layout

Along with string and wire sizing, module layout is another one of the main responsibilities for a system designer. Module layout is key for production and installation, but also for use of the roof. In the past, solar installers tried to put as many panels on the roof as possible. Recently, however, designers have taken to creating layouts that feature room on the roof for fire lanes and installation ease, while still allowing for snow clearing, and additional air-conditioner units.

Check out this comprehensive Residential Solar PV Design Guide for free: