Full-Stack Product Engineer, Ruby on Rails (m/f/d) at Solar Startup

About Us At the company, we're building the Energy OS for multi-family buildings.

Germany has over 3.3 million apartment buildings — and they are the blind spot of the energy transition.

At the same time, regulation is forcing property owners into major investment: solar is becoming mandatory, smart meters must be rolled out nationwide within five years, heating and mobility are electrifying.

The apartment building is transforming from passive real estate into an active part of the decentralised energy infrastructure.

What's missing is an integrated system that makes this transition economically viable and operationally manageable.

the company combines certified meter operation with proprietary software, enabling property owners to sell self-generated solar power directly to their tenants — simply, and without having to become an energy supplier themselves (§42b En WG).

Regulatory obligation becomes a profitable, predictable opportunity

• Double-digit returns and asset appreciation for owners,
• ~20% electricity cost savings for tenants, and
• digital infrastructure for storage, heat pumps, and flexibility.

We already manage a three-digit number of projects — including some of Germany's largest property holders and housing cooperatives — in all 16 federal states.

In the course of our seed financing, we raised €3.3M from leading impact and energy VCs (including Rubio Impact Ventures, HTGF, and Kopa Ventures).

We're now entering the next growth phase and expanding our team.

We're at the beginning of a structural market shift. Join us and help build the leading Energy OS.

Your Profile

You have 2+ years of professional experience building full-stack web applications, ideally with Ruby on Rails.

Experience in comparable frameworks (Django, Laravel, Spring Boot, Next JS) will also be considered, if you are truly motivated to learn and work with Rails.

• You have strong frontend development skills, ideally with solid fundamentals (HTML, CSS and Java Script), as well as familiarity with the Rails-specific frontend technology (Hotwire, Turbo and Stimulus) and a framework like React or Vue.
• You have an eye for UI and UX - you know interface patterns, think from a user's point of view and have worked with design systems.
• You're comfortable designing and optimizing relational database schemas (we use Postgre SQL).
• You are used to working with APIs and integrating with 3rd-party services.
• You are familiar with cloud infrastructure - Heroku, AWS, or similar - including CI/CD pipelines and basic monitoring.
• You are actively working with AI and pushing for efficient agentic setups; we are establishing Claude Code in the team and the whole company.
• You like to take ownership for the features and components you work on and you are proactive in the product development.
• You are excited about startups and want to make a real impact on the product and the company in a truly agile way.
• You are based in Berlin (or willing to relocate).

You will enjoy working in our office in Friedrichshain with the team most of the time, with the flexibility of 1-2 remote work days a week.

• You are willing to learn energy industry terms in English and German and being comfortable with some parts of the company operating mostly in German. (Team language is English.)
• Your Responsibilities

You'll be an early member of our growing product development team, working across the entire stack.

Currently that's a straight-forward Ruby on Rails app + Postgre SQL + Hotwire on Heroku which we will specialize and optimize as we're scaling.

The core functionality of the the company platform is processing smart meter measurement data for analyzing and billing solar power usage.

For this purpose, we provide landlords and tenants with a portal and automate contract management, invoicing and payment flows.

An admin interface and integration with internal tools enable the creation and management of projects by our operations team.

You focus on the users' perspectives, get involved in interface design discussions and actively shape both the product and the team.

• 1. Full-stack feature development and UI quality
• You co-design and build features across the full stack, from database to UI
• You work directly with product management, design and users to get the details right.
• You help raise the bar on frontend quality by contributing to a consistent design language, readable layouts and UI patterns that scale across the product without becoming messy.
• 2. Data processing, automation and reliability
• You work on our crucial backend processes: importing and processing of smart meter measurement data and automated billing.
• You participate in designing and maintaining the underlying server infrastructure.
• You instrument, optimize and monitor critical processes so they remain fast, reliable and dependable as we scale.
• 3. Technical design, architecture and engineering excellence
• You research, evaluate and design technical solutions to new problems together with the team.
• You contribute to our aspiration to get better and more efficient as engineers and as a team every day.
• You continuously improve our development environment and engineering processes, including adopting the right tools, workflows and AI-powered development practices.

Benefits

Competitive salary including shares based on the level of your experience.

• Real ownership: You shape the company actively from day one. Ownership means responsibility for your tasks end-to-end and the opportunity to take leadership.
• Visible impact: We ship features every day that make a difference for our customers and colleagues.
• Personal and professional growth: We have very skilled and experienced people on the team that you can learn from and we actively provide opportunities to develop your career.
• Making a difference: Our daily work reduces energy costs for tenants, advances the energy transition in residential buildings, and accelerates the economic decarbonisation of Germany's housing stock.
• Great workplace: Office in a cool co-working space in Berlin-Friedrichshain, with free drinks, cerials, fruits, and plenty of lunch options nearby.

We're a team that shares lunch, swaps ideas, welcomes new faces regularly, and genuinely listens — come help shape what comes next.

At the company, we believe that diversity strengthens both our company and society.

We do not make hiring or employment decisions based on race, religion, ethnicity, nationality, gender identity, sexual orientation, disability, or age.

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