---
title: 'Senior Software Engineer in Test at Mainspring Energy'
canonical: 'https://feeny.ai/job/senior-software-engineer-in-test-mainspring-energy-menlo-park-w2wmp8mnhv03'
type: 'job'
last_seen: '2026-09-07'
---

# Senior Software Engineer in Test at Mainspring Energy

- **Company:** Mainspring Energy
- **Location:** Menlo Park, CA
- **Compensation:** $135k–$159k
- **Work type:** onsite
- **Posted:** 2026-08-24
- **Last confirmed live:** 2026-09-07
- **Apply:** https://jobs.lever.co/mainspringenergy/fbd2184c-5c48-4d30-b8a6-8f598af9a768

## Job description

## About Mainspring

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

Job Overview Do you enjoy diving into building new automation systems and formulating new testing approaches in areas like cloud computing, networking, IoT with real time operating systems, controls, simulations (MIL, SIL, PIL), and algorithms? We combine this technology with our company vision of building a new category of power that is affordable, reliable, and targeting a net-zero carbon grid. This cornucopia of science and technology will be your daily career at Mainspring.

This is an opportunity for you to join a world-class engineering team: to build and run automated testing systems to ensure the quality of the product. This is an exciting opportunity to become part of a rapidly growing engineering team.

In this role. you will have significant influence over the quality of the product, engage with developers to understand new features and technologies, and create innovative automated testing solutions within tight requirements to solve complex scenarios with multiple components.

## Responsibilities

- Architect Automation: Design and scale robust test frameworks and CI/CD integrations
- System Validation: Create workflows to validate complex hardware/software integrations and resolve system-level bottlenecks
- Root Cause Analysis: Lead failure analysis and risk mitigation to ensure test stability and environment reliability
- Strategic Coverage: Drive risk-based testing strategies to ensure comprehensive coverage of all critical-path functionalities

## Qualifications

- Experience & Education: Bachelor’s degree in Computer Science or a related field with 6+ years of professional experience, or a Master’s degree with 5+ years in an SDET or Software Engineering role
- Engineering Mindset: A driven, self-directed contributor who views test infrastructure as a first-class product; you thrive on architecting scalable, automated systems that increase developer velocity
- Strategic Test Design: Proven track record of leading complex automation projects from design to implementation, with the foundational ability to perform deep-dive manual exploratory testing and technical test case design
- Technical Versatility: Strong hands-on experience developing in Python and C++, with the flexibility to navigate and contribute to diverse codebases as the project requires
- AI Workflow Ownership: Demonstrated proficiency in leveraging AI coding assistants as a force multiplier for productivity, combined with the professional judgment to challenge and expand upon AI-generated solutions to ensure system integrity and long-term maintainability

Does your experience not meet all of our posted requirements? Studies have shown that some people are less likely to apply to positions unless they meet every listed requirement. At Mainspring, we are committed to building a diverse, inclusive, flexible, and collaborative environment, so if you want to help us transition the world to clean and affordable electricity, and don’t meet all posted requirements for a particular role, we’d still love to hear from you. Mainspring can sometimes be flexible enough to shift responsibilities for the right person, or otherwise identify open or upcoming roles that may better fit your professional background. In more traditional words, Mainspring Energy, Inc is an Equal Opportunity Employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, sex, sexual orientation, gender identity, national origin, or protected veteran status and will not be discriminated against on the basis of disability. This compensation and benefits information is based on Mainspring Energy's estimate as of the date of publication and may be modified in the future. We generally do not negotiate on salary once we have made an offer. The level of pay within the range will depend on a variety of job-related factors that may include location, relevant prior experience and/or education, or particular skills and expertise. New hires joining the company tend to be paid within the starting base pay range noted above, with opportunities to increase pay over time based on development of additional skills, competencies, and company-specific knowledge.

## About Mainspring Energy

## Company Overview
- **One-liner**: Mainspring Energy designs and manufactures fuel-flexible linear generators that provide low-emission, dispatchable onsite power for utilities, data centers, and industrial customers.
- **Entity Type**: Private (Series F)
- **Headquarters**: Menlo Park, California, United States
- **Founded**: 2010
- **Founders**: Shannon Miller

## Core Business
- Primary industry: Electric Power Generation
- Target customers: B2B – utilities, data center developers, enterprise, industrial
- Mission statement: "Redefining how local power is delivered to capacity constrained companies and communities" – enabling clean, reliable, and fuel-flexible power.

## Products & Services
- **[Linear Generator (LGen)]**: A flameless, fuel-flexible generator that converts gaseous fuels (natural gas, biogas, hydrogen, propane) into electricity with near-zero NOx emissions. Modular (0.25 MW per unit), fast-ramping (0-100% dispatchable), 46% electrical efficiency (LHV). Standardized 2.5 MW configuration (10 units). Suitable for grid-parallel or grid-independent operation, microgrids, and balancing renewables.

## Market Standing
- **Valuation/Market Cap**: Not disclosed (private company)
- **Key Metrics**: Annual revenue $117M (latest fiscal year); total funding $813M; 407 employees
- **Notable Investors/Partners**: General Catalyst (led Series F, 2025, $258M), Lightrock (led Series E, 2022, $140M), BloombergNEF (grant), and others.
- **Growth Signals**: Powering the largest U.S. EV truck charging depot; >1 GW of capacity trusted by Fortune 500 companies and utilities; headcount growing +3.4% YoY; job postings up +121.4% YoY (62 active openings); recently expanded into data center market.

## Competitive Advantages
- **Fuel Flexibility**: Single generator can seamlessly switch between natural gas, RNG, hydrogen, and propane without hardware retrofits.
- **Near-Zero Emissions**: <1.5 ppm NOx (0.05 lb/MWh) – meets stringent air quality standards.
- **Dispatchability**: 0-100% load following, grid-independent operation, capable of firming renewables.
- **Low Maintenance**: Only two moving parts, no oil changes, modular design reduces downtime.
- **High Efficiency**: 46% electrical efficiency (LHV) across all scales.
- **Fast Deployment**: Factory-built, skid-mounted units enable rapid installation.

## Strategic Focus
- Scaling manufacturing and deployment to meet growing demand from data centers and utilities.
- Advancing hydrogen and biogas compatibility to support long-term decarbonization.
- Expanding standardized 2.5 MW configurations to lower installed cost and accelerate timelines.
- Building a diverse, cross-disciplinary team to drive innovation in power generation.

## Why Work Here
- Culture of inclusion, respect, and collaboration across engineering, operations, and field teams.
- Emphasis on growth: "We invest in your growth because progress requires people who keep getting better."
- Hybrid/Remote options: headquarters in Menlo Park, manufacturing facilities, and remote field service roles.
- Active hiring across engineering (mechanical, electrical, software), operations, supply chain, and field service.
- Competitive salary ranges (e.g., Engineer ~$107k, Controls Engineer ~$109k, Manufacturing Engineer ~$91k) plus benefits.
- Diverse talent origins from Tesla, Stanford, Apple, SunPower, and other top clean energy companies.

## Sources
1. [mainspringenergy.com/company](https://www.mainspringenergy.com/company)
2. [mainspringenergy.com/careers](https://www.mainspringenergy.com/careers)
3. [jobs.lever.co/mainspringenergy](https://jobs.lever.co/mainspringenergy)
4. [linkedin.com/company/mainspringenergy](https://www.linkedin.com/company/mainspringenergy)
5. [mainspringenergy.com/product](https://www.mainspringenergy.com/product)

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