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Principal Mechanical Engineer – Energy Infrastructure Projects

United States

ON.energy is building the power infrastructure that makes the AI era possible. As AI demand surges past what the grid and traditional data centers can support, ON.energy provides a new class of power technology proven at gigawatt scale and trusted by the world’s leading cloud and AI companies. Our systems are already deployed across 2.5 GW of hyper-scale campuses, validated by top U.S. national labs, and certified for grid-safe operation by major utilities. With real products in the field, we’re scaling faster than the grid can, transforming power from a bottleneck into a competitive advantage for the companies building the future.

Role Overview

The Principal Mechanical Engineer is a recognized expert in mechanical, structural, thermal, and fluidic systems, serving as a senior individual contributor in design, analysis, and validation activities within ON.Energy's product engineering organization. This role owns the development and implementation of mechanical standards, analytical processes, and validation frameworks that directly influence product reliability, structural safety, and field performance. The Principal ME operates with significant autonomy, collaborates closely with BESS, Power Electronics, Controls, and field engineering teams, and communicates technical findings and risk to engineering leadership and external stakeholders. This is a product-focused role requiring someone equally comfortable at the whiteboard and in the field.


Key Responsibilities:

Structural Analysis & Mechanical Validation

  • Perform and oversee structural stress, fatigue, and vibration analysis for mechanical assemblies, enclosures, and supporting infrastructure across ON.Energy's product portfolio.
  • Lead or review FEA models and reports to validate mechanical designs under static, dynamic, thermal, and seismic loading conditions.
  • Ensure mechanical and structural safety under operational loads, transportation loads, and applicable environmental conditions.
  • Evaluate failure modes and translate findings into design improvements that enhance product durability, reliability, and lifecycle performance.

Thermal & Environmental Systems

  • Lead thermal design activities for enclosures, including HVAC and fluidics sizing calculations, temperature limit identification, humidity management, and mitigation strategies.
  • Validate cooling and heating system performance across a range of environmental conditions, including extreme heat, cold, high humidity, and coastal/saline environments.
  • Develop simulation-backed recommendations for thermal and environmental design improvements using FEA/CFD tools.

Specifications Development & Operational Planning

  • Establish and maintain mechanical engineering specifications, analytical processes, and validation methodologies that govern hardware development and deployment.
  • Develop and implement new processes or engineering specifications with measurable impact on product quality, structural safety, and field reliability.
  • Ensure designs are validated against applicable codes and standards (e.g., IBC, ASCE 7, NFPA, IEC, UL) and that compliance is documented throughout the design lifecycle.

Cross-Functional Collaboration & Design Advisory

  • Collaborate with BESS, Power Electronics, and Controls teams to ensure integrated system-level mechanical performance.
  • Participate in product design sprints and stage-gate reviews as a structural and mechanical SME, identifying risks before they reach the field.
  • Provide technical input during design iterations based on lessons learned from project engineering, installation, commissioning, and O&M activities.
  • Support development and review of mechanical documentation including calculations, reports, specifications, and as-built drawings.

Communication & Field Engagement

  • Communicate structural risks, design decisions, and engineering trade-offs clearly to both technical teams and non-technical stakeholders, including engineering leadership and external clients.
  • Willing to travel up to 20% to support product FAT inspections and site commissioning witnessing.


Required Skills & Experience

  • Bachelor's degree in Mechanical Engineering or related technical field.
  • 12+ years of hands-on structural and mechanical engineering experience in product-based, project-based, or industrial settings.
  • Strong experience performing stress analysis, fatigue analysis, and vibration assessment on mechanical assemblies and enclosures.
  • Demonstrated experience with thermal design of enclosures, including HVAC system design and environmental management.
  • Proficiency with FEA tools (e.g., SolidWorks Simulation, ANSYS) for structural and thermal validation.
  • Proven ability to develop or improve mechanical standards and processes with tangible impact on product outcomes.
  • Ability to interpret engineering drawings and develop detailed calculations and technical reports.
  • Strong communication skills across both technical and non-technical audiences.

Preferred Experience:

  • Experience in battery energy storage, medium voltage UPS, power conversion, power generation, or mission-critical infrastructure.
  • Panel building mechanical design experience for power and controls/IT equipment.
  • Familiarity with seismic zone design requirements and site-specific structural compliance.
  • Master's degree in Mechanical Engineering or related field.

For US-based roles - What you’ll get:

  • Competitive salary + annual performance-based bonus eligibility
  • Medical, dental, and vision insurance
  • 401(k) with company match
  • Paid time off and company holidays 

For Mexico-based roles - What you’ll get:

  • Competitive salary + annual performance bonus eligibility
  • Christmas Bonus (Aguinaldo): 30 days
  • Major medical expenses and life insurance
  • Paid time off and holidays (per local policy)

For all roles:

  • Professional development and growth opportunities
  • Opportunity to grow with a mission-driven team shaping the future of clean energy
  • Equal Opportunity: ON.energy is committed to equal employment opportunity and to maintaining a work environment free of harassment, discrimination, or retaliation.
  • Accommodations: If you need an accommodation during the application process, email recruitment@onenergystorage.com
  • Benefits vary by role and location and are subject to change.

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