Software Optimisation Engineer

Job title: Software Optimisation Engineer

Location: UK Hybrid (minimum working 2 days per week in our London office)

Contract Type: Permanent, Full-Time

Salary Grade: Grade C £56,761 to £69,015

About us

We are a climate analytics nonprofit established in 2021. We provide system modelling data, software and analysis to support energy transition planning and decision-making. We are grant-funded by the Quadrature Climate Foundation, Google.org, Sequoia Climate Foundation, Bloomberg Philanthropies, European Climate Foundation, among others. Our data, software and analysis is used by developers, financiers, planners and think tanks internationally.

At TransitionZero, we understand that diversity is an essential component of a successful team, whether that be diverse ways of thinking, personal or professional backgrounds and skills. We aim to be the most talented nonprofit in our vertical, spearheading innovative data solutions through our culture of inclusivity and adaptability. Now we are looking for a software optimisation engineer to join our tech team.

Our people are our greatest asset, and the diverse experience, skills and perspectives individuals bring to our organisation are the driving force of our success. We will therefore consider all qualified applicants in the recruitment process as we welcome all the unique qualities and experiences that make you, you.

About the role

We are building a data and modelling platform that makes energy systems analysis auditable, accessible, and reproducible. Our platform is the entry point to all of our data and analysis, including satellite-derived greenhouse gas emissions intelligence, forecast and weather data, and our energy systems modelling capability. Users can self-serve data and develop actionable insights through a browser-based interface, API, and Python client library.

The Software Optimisation Engineer ensures TransitionZero’s energy modelling services are robust, scalable, and production-ready, enabling decision-makers to trust and act on our insights. By optimising energy system models for performance and reliability, and embedding best practices in software engineering, this role directly supports our mission to make energy analysis auditable, accessible, and reproducible. Their work turns complex models into reliable services that power better investment and policy decisions for the energy transition.

Responsibilities

• Build and maintain backend services that expose energy modelling capabilities through documented APIs (OpenAPI 3.1).
• Develop production-grade software with CI/CD pipelines, testing, observability, and containerisation.
• Implement and tune capacity expansion and dispatch models.
• Optimise algorithmic performance (runtime, memory usage, solver convergence).
• Ensure scalability from small exploratory runs to national and regional-scale simulations.
• Select and apply the most appropriate optimisation techniques, using exact methods such as linear and mixed-integer programming where tractable, and heuristics or metaheuristics to approximate or accelerate solutions when problems become too large or complex for exact solvers.
• Collaborate with analysts to ensure models capture actual system operation and market dynamics.
• Work with engineers on data ingestion, cloud execution, and delivering results to the platform front-end.
• Ensure modelling workflows are robust, scalable, and responsive, providing predictable performance under varying workloads.
• Contribute to TransitionZero’s platform vision of delivering modelling as-a-service, enabling decision-makers to integrate modelling into their workflows.
• Continuously improve optimisation performance, service reliability, and engineering practices.

About you

• A software engineer with optimisation expertise. You care about production readiness and algorithmic efficiency.
• Deeply interested in energy system modelling and skilled in making models robust, scalable, and performant.
• Curious, collaborative, and proactive - you thrive in multidisciplinary teams.
• Adaptable and open-minded - you are comfortable trying new approaches, including AI tools, to improve workflows.
• Have a continuous improvement mindset - you reflect on how things can be done better and act to raise quality, efficiency, and impact.
• Motivated by purpose: you want your skills to directly contribute to decarbonisation and the clean energy transition.

Skills & experience

Essential

• Strong programming skills in Python, with experience delivering production-quality software.
• 3+ years’ experience in energy systems modelling (capacity expansion and dispatch).
• Proven experience with PyPSA; familiarity with OSeMOSYS, TIMES/MARKAL, or MESSAGE is a plus.
• Proven experience with optimisation solvers (e.g., Gurobi, HiGHS, etc.).
• Deep understanding of linear and mixed-integer programming, plus experience optimising algorithmic performance.
• Familiarity with CI/CD pipelines, testing frameworks, Git workflows, observability, and containerisation (Docker).
• Ability to design services that are responsive, resilient, elastic, and message-driven.

Beneficial

• MSc or PhD in a relevant STEM field (energy systems, applied mathematics, computer science).
• Experience with heuristics/metaheuristics or ML-based optimisation.
• Knowledge of geospatial data handling (GeoPandas, Uber H3).
• Experience with strongly typed languages (Java, Kotlin, Go, C++) for performance-critical optimisation code.
• Experience running large-scale models on cloud or HPC infrastructure.

Salary & benefits

• Competitive salary based on experience
• Enhanced competitive pension scheme- auto-enrollment from day 1
• 25 days annual leave (excluding UK public holidays) and an additional discretionary days off such as over the festive period
• 20 days annual allowance to work from anywhere in the world
• Hybrid working and core working hours model
• Allowance to set up your home office
• Annual budget and dedicated leave time for relevant training courses
• Enhanced gender-neutral parental leave (16 weeks fully paid)
• Private healthcare following successful completion of the probation period
• Yearly team offsites

Our commitment to diversity, equity, and inclusion

Studies have shown that some people from marginalised or underrepresented groups are less likely to apply to a role unless they meet all of the hiring guidelines or qualifications. Whoever you are, even if you don't meet all of the criteria, if you can demonstrate a variety of skills and experience relevant to this role, we encourage you to apply as you might just be the candidate we hire! At TransitionZero, we're looking for people who are genuinely passionate about what they do, and we welcome all people, regardless of their background.

If you would like to discuss any reasonable adjustments to the application or hiring process that may better facilitate your participation, please contact our People Team (people@transitionzero.org) for an informal chat. We will make every effort to respond to your request for assistance as soon as possible.