On.Energy Software Engineer interview questions & guide 2026

Preparing for an interview at On.Energy requires a dual focus on software fundamentals and physical system integration. You must demonstrate that you can write clean, reliable code while respecting the physical constraints of electrical hardware.

Technical & Domain Expertise – You must show a deep understanding of industrial protocols, control theory, and energy storage systems. Expect to explain the mechanics of lithium-ion batteries, inverters, and how software coordinates their behavior. Be prepared to discuss your hands-on experience with tools like PLCs, SCADA databases, and scripting languages.

Operational Troubleshooting – Interviewers care deeply about how you solve problems when things go wrong. You should structure your answers to technical scenarios logically, starting with the most likely root causes, explaining your diagnostic tools (such as Wireshark or register scanners), and detailing how you implement permanent fixes rather than temporary workarounds.

Safety & Quality Mindset – Working with high-voltage battery systems carries inherent risks. You must weave a safety-first philosophy into all your answers. Highlight your familiarity with industrial safety standards, lock-out/tag-out (LOTO) procedures, and how you write software defensively to prevent hardware damage or thermal events.

Collaborative Execution – Delivering a BESS project requires seamless teamwork across software, hardware, civil engineering, and project management. You must demonstrate that you can translate complex software concepts to non-technical stakeholders and work constructively with external partners, such as utility operators and equipment manufacturers.

The interview process at On.Energy is structured to evaluate both your technical execution capabilities and your alignment with the company's fast-paced, collaborative culture. The process is designed to mimic real-world engineering challenges you will face on the job, focusing on practical problem-solving rather than abstract academic puzzles.

The journey typically begins with an initial conversational screen with a recruiter to discuss your background, career goals, and basic alignment with the role's requirements. Following this, you will progress to a technical screen focusing on your core domain—whether that is controls engineering, software development, or network architecture. This is followed by a deeper panel interview or a practical scenario-based session where you will walk through system designs, troubleshooting exercises, or code reviews with senior members of the engineering team.

The visual timeline above outlines the typical progression from your initial contact to the final offer stage. Candidates should use this roadmap to pace their preparation, focusing first on high-level system concepts and behavioral stories, before diving deep into technical protocols and system architecture for the panel stages. Note that the exact number of technical rounds may vary slightly depending on whether the role is heavily field-focused (like Commissioning) or development-focused (like EMS Software Engineering).

To succeed in the On.Energy interview process, you must master several key technical domains. The engineering team evaluates candidates across three primary pillars.

EMS & SCADA Systems

This area evaluates your ability to manage, configure, and optimize the software layer that monitors and controls energy storage assets. You must understand how data flows from physical meters and battery modules up to cloud-based monitoring platforms.

Be ready to go over:

• Data Acquisition – How to ingest high-frequency telemetry data without overwhelming edge processors or network bandwidth.
• Protocol Translation – How to convert various industrial protocols (e.g., Modbus RTU to Modbus TCP or MQTT) to ensure seamless communication.
• HMI and Alarm Management – Designing clear, actionable human-machine interfaces and configuring alarm thresholds to prevent alert fatigue for operators.
• Advanced concepts (less common) – Integrating historical databases (TSDBs) at the edge, implementing local data buffering for internet outages, and configuring deadband settings for telemetry reporting.

Example questions or scenarios:

• "Design a schema for a SCADA database that needs to log state-of-charge (SoC) and cell temperature data from 10,000 battery cells every second."
• "How would you diagnose a high-latency issue in an EMS that is causing delayed commands to the site inverter?"

Control Systems & PLC Programming

For roles involving direct hardware control, you must demonstrate a strong command of control theory, industrial automation, and real-time state execution.

Be ready to go over:

• PLC Logic & Languages – Proficiency in IEC 61131-3 languages (such as Structured Text or Ladder Logic) and state-machine design.
• Closed-Loop Control – Implementing and tuning PID controllers for active/reactive power dispatch and temperature regulation.
• Interlocking & Safety Logic – Designing fail-safe hardwired and software interlocks to protect equipment and personnel.
• Advanced concepts (less common) – Implementing frequency-droop control, black-start sequences, and microgrid islanding transitions in control software.

Example questions or scenarios:

• "Walk through the state machine logic required to safely execute an emergency shutdown (ESD) of a 10MW BESS."
• "How would you program a PLC to balance the state of charge across three independent battery trailers operating in parallel?"

Network & OT Infrastructure

Industrial control systems rely on robust, secure, and highly reliable local networks. You will be evaluated on your ability to design and maintain these critical communication pipelines.

Be ready to go over:

• Industrial Networking – Configuring managed switches, VLANs, and routing protocols in an industrial environment.
• Cybersecurity (OT) – Implementing defense-in-depth strategies, firewalls, secure VPN tunnels, and access control lists (ACLs).
• Physical Media – Understanding the practical limitations and use cases of fiber optics, copper Ethernet, and serial communications (RS-485) in high-noise electrical environments.
• Advanced concepts (less common) – Implementing NERC CIP compliance controls, configuring intrusion detection systems (IDS) for OT networks, and setting up redundant network topologies (such as MRP or RSTP).

Example questions or scenarios:

• "How do you isolate utility-facing dispatch networks from the internal battery management system network?"
• "Describe how you would troubleshoot electromagnetic interference (EMI) affecting an RS-485 serial communication link on-site."

As a Software Engineer (or Systems/Controls/Deployment Engineer) at On.Energy, your daily responsibilities will span the entire lifecycle of energy storage projects, from early-stage design to long-term operational support.

You will spend a significant portion of your time configuring, testing, and deploying Energy Management System (EMS) software and PLC control logic. This involves translating complex engineering requirements—such as utility interconnection agreements and battery warranty constraints—into reliable, deterministic code. You will work closely with hardware engineers to select and validate edge controllers, meters, and communication gateways.

Collaboration is central to this role. You will act as the technical bridge between internal project managers, hardware vendors, and external utility engineers. On any given day, you might be in a meeting defining Modbus register maps with an inverter manufacturer, writing Python scripts to automate testing, or coordinating with a field commissioning engineer to debug a network routing issue on-site.

Additionally, you will support active field operations. When systems are being commissioned or experience operational issues, you will provide critical tier-3 engineering support. This means analyzing system logs, diagnosing communication dropouts, and deploying software patches to live, operating assets without disrupting their service to the grid.

To be competitive for a Software Engineer position at On.Energy, you must possess a strong blend of software capability and industrial systems knowledge.

• Must-have skills – Proficiency in a programming or scripting language (such as Python, C++, or Structured Text), deep familiarity with industrial communication protocols (Modbus TCP/RTU, DNP3, CAN bus), and a solid understanding of IP networking (subnets, routing, firewalls).
• Nice-to-have skills – Experience with specific PLC platforms (such as Sel, WAGO, Beckhoff, or Allen-Bradley), familiarity with SCADA platforms (such as Ignition), knowledge of power systems engineering, and direct experience working with utility-scale inverters or battery chemistry.
• Experience level – Depending on the seniority of the role, requirements range from 2–5 years of experience for mid-level engineers to 8+ years for senior project and power electronics roles. A background in renewable energy, industrial automation, or maritime/aerospace control systems is highly valued.
• Soft skills – Exceptional troubleshooting skills, the ability to communicate complex technical details clearly to non-technical stakeholders, a high degree of adaptability, and a relentless commitment to physical safety and software quality.

Q: How much travel is required for these roles? A: Travel expectations vary significantly by specific title. Commissioning and Deployment roles can require up to 30% to 50% travel to project sites for active start-up activities. Pure software development or senior project engineering roles are typically hybrid or remote with minimal travel (10% to 15%) primarily for key project milestones or team alignment.

Q: Does this role focus more on pure software development or systems integration? A: It is a hybrid of both. While you will write code (primarily Python, PLC logic, and scripting), a massive component of the role is systems integration—ensuring that your code successfully interfaces with physical hardware, meters, and utility networks.

Q: What differentiates a successful candidate at On.Energy? A: The most successful candidates are those who possess "hardware empathy." They understand that software bugs in this domain do not just cause application crashes; they can cause physical damage to multi-million dollar physical assets. A rigorous, disciplined approach to testing and safety is highly valued.

Q: What is the typical timeline for the hiring process? A: The process typically moves efficiently, taking between 3 to 5 weeks from the initial recruiter screen to a final decision, depending on candidate availability and the scheduling of technical panels.

Q: Is remote work supported? A: Yes, several engineering positions (especially senior and specialized design roles) offer remote flexibility. However, roles tied to deployment, commissioning, and physical testing are often hybrid or tied to specific regional hubs like Houston, Atlanta, or Reston to facilitate laboratory and site work.

To truly stand out during your interviews, keep these practical, insider tips in mind:

• Emphasize Your Troubleshooting Methodology: When asked technical scenario questions, do not just jump to the answer. Walk the interviewer through your logical debugging process. Start with the physical layer (cables, power), move to the network layer (pings, IP routing), and finally to the application layer (register maps, protocol handshakes).
• Highlight Safety at Every Turn: If you are discussing a time you solved a problem on-site or designed a system control loop, explicitly mention the safety protocols you followed or designed (such as LOTO, wearing proper PPE, or implementing software-level watchdog timers).

• Showcase Cross-Disciplinary Knowledge: If you are a software-focused engineer, demonstrate that you understand the basic electrical concepts of a BESS (e.g., active vs. reactive power, DC/AC conversion, state of charge). If you are a controls engineer, show that you write clean, modular, and well-documented code.

A Software Engineer role at On.Energy offers a unique opportunity to apply your technical skills directly to the front lines of the global energy transition. By building and deploying the software that controls massive battery storage installations, you will actively solve some of the most complex integration and grid-stability challenges of our time.

To prepare effectively, focus your energy on mastering industrial communication protocols, structuring clear troubleshooting narratives, and demonstrating a deep respect for physical safety and system reliability. Your ability to bridge the gap between abstract software logic and physical hardware execution will be your greatest asset during the interview process.

The salary data reflects the diverse range of engineering disciplines housed under the "Software Engineer" umbrella at On.Energy. Commissioning and deployment roles generally start in the $75,000 to$110,000 range, while specialized controls, OT, and Senior Project Engineering roles command salaries up to $164,000. Use this compensation insight to align your expectations based on your specific technical specialization and experience level.

For more detailed interview preparation resources, interactive practice questions, and community insights from candidates who have successfully navigated the clean energy interview landscape, explore the additional tools available on Dataford. With focused preparation, you can confidently showcase your expertise and secure your place on the On.Energy engineering team.