Question 1
Difficulty: medium
How do you approach designing a solar PV system for a commercial site from the first site visit to final layout?
Sample answer
I start by treating the site visit as a mix of engineering work and risk discovery. First I review the load profile, utility interconnection requirements, roof or ground constraints, shading sources, and any structural or permitting issues that could affect the design. On site, I verify dimensions, equipment access, conduit paths, and safety concerns, because small field details often change the layout more than the desktop drawings do. Then I build the system around performance and constructability at the same time. I size the array, select the inverter architecture, check stringing limits, and estimate expected production using site-specific assumptions rather than generic numbers. I also coordinate early with structural, electrical, and permitting teams so the design can actually get built. Before finalizing, I review every major assumption, from tilt and spacing to voltage drop and fire code clearance, and I make sure the design balances energy yield, cost, and long-term maintainability.
Question 2
Difficulty: medium
Tell me about a time you identified a design issue in a solar project before construction. What did you do?
Sample answer
On one project, I noticed during the final design review that the proposed inverter location created two problems: the conduit run was longer than expected, and the placement would have made maintenance access difficult during hot weather. The issue was not obvious in the initial layout because the roof plan looked straightforward on paper. I flagged it, then did a quick field verification and rechecked the one-line and equipment spacing against the site constraints. Rather than just pointing out the problem, I brought two alternate options with me: moving the inverter bank closer to the main service point and revising the string layout to keep electrical losses acceptable. I worked with the project manager and installer to compare cost, production impact, and schedule impact. We changed the layout before procurement, which saved rework and avoided an unnecessary code review delay. That experience reinforced for me that good solar engineering means catching practical issues early, not just producing clean drawings.
Question 3
Difficulty: medium
How do you evaluate shading and its impact on PV system performance?
Sample answer
I treat shading as both a modeling problem and a field problem. First I identify the likely sources: nearby buildings, HVAC units, parapet walls, trees, utility hardware, and seasonal changes in sun angle. Then I use site data and layout tools to map when and where shading will occur across the day and year, because the timing matters as much as the amount. I pay close attention to partial shading, since even a small obstruction can affect an entire string depending on the system design. From there I compare different mitigation strategies, such as repositioning modules, adjusting tilt, using module-level power electronics, or modifying the string configuration. I do not assume technology alone will solve the issue; sometimes the best answer is simple spacing or relocation. Finally, I translate the shading impact into expected energy loss so the client can make a clear decision based on economics, not guesswork. That keeps the design honest and practical.
Question 4
Difficulty: medium
What factors do you consider when selecting inverters and other major components for a solar project?
Sample answer
I look at component selection as a balance between electrical fit, reliability, serviceability, and project economics. For inverters, I start with the system architecture: string, central, or hybrid, depending on project size, layout, and operational goals. Then I check voltage windows, DC-to-AC ratio, temperature performance, grid support features, and compliance with utility and code requirements. I also pay attention to maintenance access, warranty terms, manufacturer support, and whether the equipment has a strong track record in similar environments. For modules, I look at efficiency, degradation rates, temperature coefficient, mechanical load ratings, and bankability, because the cheapest option is rarely the best over 25 years. For balance-of-system components, I verify compatibility and installation simplicity. I try to avoid overcomplicating the design with niche products unless there is a clear benefit. My goal is always to choose components that perform well, can be sourced reliably, and will be easy for the operations team to support long after commissioning.
Question 5
Difficulty: hard
Describe how you would troubleshoot a solar PV system that is underperforming after commissioning.
Sample answer
I would start by separating the problem into possible categories: design, installation, equipment, controls, environmental conditions, or grid-related issues. First I compare the monitored output against expected production using weather data, irradiance, and system design assumptions to confirm the underperformance is real and not just a data issue. Then I check inverter alarms, string performance, communication errors, and clipping patterns. If the system is array-level monitored, I look for module or string imbalances that could point to wiring mistakes, damaged equipment, or shading problems. I also review commissioning records, because issues like reversed polarity, loose terminations, incorrect settings, or CT errors can hide in plain sight. If needed, I would inspect the site physically with infrared imaging, IV curve tracing, and targeted electrical tests. I like to move from fastest validation to deeper diagnostics so we do not waste time. Most importantly, I document every finding clearly so the corrective action is traceable and the same issue does not repeat later.
Question 6
Difficulty: hard
How do you ensure a solar design complies with electrical codes, fire safety rules, and local permitting requirements?
Sample answer
I build compliance into the design process from the beginning instead of treating it as a final checklist. I start by identifying the applicable code set, utility interconnection rules, fire marshal requirements, and any local amendments that can affect layout or equipment placement. Then I design with those constraints in mind, especially for conductor sizing, overcurrent protection, rapid shutdown, access pathways, labeling, grounding, and equipment clearances. I also pay attention to roof access routes, setbacks, and the way the system interacts with existing building infrastructure. To avoid surprises, I like to review the design with permitting stakeholders early if the project is complex or unusual. I keep a code compliance matrix so every major requirement can be traced to a drawing note or equipment choice. That approach helps during permit review and later during inspection, because the project team can quickly show how the design satisfies the requirements. It also reduces rework, which is one of the biggest schedule risks in solar projects.
Question 7
Difficulty: medium
Tell me about a time you had to explain a technical solar issue to a non-technical stakeholder.
Sample answer
I worked on a project where the client was concerned that a lower-than-expected estimated annual output meant the design was failing. The issue was actually tied to realistic assumptions about shading, temperature losses, and inverter clipping, but those terms did not mean much to them. Instead of going deeper into engineering jargon, I explained the system using simple comparisons: how the array would perform on ideal days versus typical days, and why nameplate size is not the same as guaranteed output. I showed them a few scenarios side by side so they could see the impact of different design choices, including the cost of removing a shading source versus accepting a modest annual loss. That helped shift the conversation from anxiety to decision-making. They ended up approving the design because they understood the trade-offs clearly. I find that good communication in solar engineering is about translating technical constraints into business outcomes without oversimplifying the facts.
Question 8
Difficulty: medium
How do you handle a situation where the contractor wants to change the design in the field?
Sample answer
I am open to field changes if they improve constructability and do not compromise performance, safety, or compliance. The first thing I do is ask what is driving the change: a hidden obstruction, equipment availability, labor efficiency, or an error in the original plan. Then I evaluate the proposed change against the design intent. I look at electrical impact, code compliance, structural implications, production effect, and any permitting consequences. If the change is reasonable, I document it quickly and get the right approvals so the team can keep moving. If it introduces risk, I explain the issue clearly and offer an alternative rather than just saying no. I have found that the best field decisions come from a respectful back-and-forth between engineering and construction. That way the installer feels supported, the project stays on schedule, and we avoid making a fast change that creates a long-term problem in operations or inspection.
Question 9
Difficulty: hard
What metrics do you use to determine whether a solar project is financially and technically viable?
Sample answer
I look at both technical yield and financial return because a project can be elegant on paper and still miss the business case. Technically, I review annual energy production, performance ratio, shading losses, degradation, availability assumptions, and interconnection limitations. I also check whether the site conditions support the expected output over the project life. Financially, I focus on levelized cost of energy, simple payback, internal rate of return, incentive eligibility, O&M expectations, and any demand-charge or tariff benefits the system can capture. For larger projects, I also think about schedule risk, procurement timing, and how likely the design is to need revisions during permitting. I like to stress-test the assumptions rather than rely on a single optimistic case. If a project only works under perfect conditions, it is not really viable. My goal is to make sure the technical design supports a strong economic case and that the economic model reflects real-world engineering decisions, not idealized numbers.
Question 10
Difficulty: easy
Why do you want to work as a Solar Engineer, and what makes you effective in this role?
Sample answer
I enjoy solar engineering because it sits at the intersection of technical problem-solving, real-world impact, and fast-moving project work. A good solar project is never just about drawings or calculations; it requires judgment, collaboration, and a willingness to adjust when site conditions or client goals change. That is the kind of work I like. I am effective in this role because I am detail-oriented without losing sight of the bigger picture. I check the numbers carefully, but I also think about constructability, code compliance, and the people who will actually install and maintain the system. I communicate well with both technical and non-technical teams, which helps projects move faster and with fewer misunderstandings. I also stay practical: I want designs that perform well, are safe, and can be built efficiently. Solar is a field where good engineering directly supports clean energy delivery, and that combination of technical challenge and meaningful outcome is what motivates me most.
