Senior Product Performance Engineer

Mainspring is seeking a rigorous, curious, and highly motivated Product Performance Engineer to own the performance of our Linear Generator. Reporting directly to the VP of Test Engineering, you will combine hands-on experimental work with in-depth data analysis to characterize, understand, and improve all aspects of the Linear Generators performance with emphasis on power output, efficiency, and emissions profiles. Your central mission is to make sure our products meet the performance targets defined in our internal Product Requirements Document (PRD), and to give engineering teams the insight they need to close any gaps. This role is ideal for an engineer or researcher with deep expertise in thermodynamics, power generation who wants to apply it to a first-of-its-kind product in a fast-paced development environment., As the Product Performance Engineer at Mainspring Energy, you will:

• Own the measurement and tracking of product performance, including power, efficiency, and emissions, against the targets defined in the PRD
• Identify gaps between measured performance and PRD targets, and drive cross-functional efforts to close them
• Design and execute experiments on Linear Generator test units, working hands-on with technicians and the test team to set up, instrument, and run studies
• Build and maintain Python-based analysis tools and pipelines to process large test datasets, quantify performance, and identify trends and root causes
• Apply first-principles thermodynamic and heat release analysis to explain observed performance
• Communicate results clearly to design engineering teams, and make data-driven recommendations that guide design decisions
• Develop and improve test methods, instrumentation, and processes to support performance validation on next-generation products

• PhD in mechanical engineering, aerospace engineering, chemical engineering, physics, or a related field, or a Master’s degree with several years of applicable industry or research experience
• Deep expertise in thermodynamics/power generation, with the ability to apply it to real hardware and experimental data
• Excellent data analysis skills in Python (e.g., pandas, NumPy, SciPy), including working with large, noisy experimental datasets
• Hands-on experience designing and executing experiments involving instrumentation and emissions testing
• Strong communicator with a collaborative mindset, comfortable presenting findings to leadership and working across teams
• Strong organizational skills and the ability to manage multiple priorities against deadlines

This position is onsite at our Menlo Park HQ. The salary will be adjusted to reflect local market conditions based on employee location as well as the experience of the employee. Along with the base salary, Mainspring offers pre-IPO RSU’s + benefits.

Mainspring Energy manufactures and delivers fuel-flexible, low-emissions local power solutions that rapidly add new capacity and deliver reliable, affordable, and sustainable electric power. The company began commercial shipments of its Mainspring Linear Generators in 2020 and today has hundreds of megawatts in advanced development and field operations for leading Fortune 500 companies, data centers, and utilities. Mainspring also partners with global energy leaders including AEP, NextEra Energy Resources, Schneider Electric, and more.

The core values that ground our work, guide our decisions, and connect us together:

• Pragmatic Optimism
• Excellence without Ego
• Proactive Collaboration