Frontend Software Engineer in London

About the Role

We are looking for a Frontend Engineer to join our interface team and help shape the future of Scenario Builder. This is an opportunity to work on a modern, greenfield frontend codebase built from the ground up using React, TypeScript, and contemporary frontend practices. You’ll be building new capabilities, improving the foundations of the product, and helping define how users interact with complex energy system models.

You will work closely with product, design, backend engineers, AI engineers, and energy specialists to build intuitive experiences over large datasets and complex modelling workflows. From data-heavy interfaces and interactive visualisations to new AI-powered capabilities, you will have the opportunity to take ownership of the features you build and see your work directly influence how users solve important energy challenges. You'll have significant autonomy, the chance to solve challenging technical problems, and the ability to see your contributions make a visible impact in a small team.

Responsibilities

• Frontend Development
  • Deliver frontend features from implementation through to release, working closely with product and design to build high-quality user experiences.
  • Build and deliver frontend capabilities for Scenario Builder using React and TypeScript.
  • Implement complex UI patterns including data tables, filtering workflows, virtualised lists, and interactive data visualisations.
  • Contribute to the evolution of our frontend architecture by building reusable, composable components and patterns.
  • Apply performance optimisation techniques when working with large datasets and visualisation-heavy workloads.
• Quality & reliability
  • Maintain high standards of code quality through testing, code reviews, documentation, and continuous improvement.
  • Diagnose and resolve bugs, usability issues, and performance problems in production.
  • Contribute to modern frontend engineering practices, including pull request workflows, CI/CD pipelines, and automated testing.
• Product & design collaboration
  • Work closely with product and design to shape solutions, balancing user needs, technical feasibility, and implementation trade-offs.
  • Collaborate with backend engineers on API design, integration, and data workflows.
  • Provide technical input during planning, refinement, and product decision-making.
• Delivery
  • Work within an agile team to break down ideas into deliverable features and contribute to sprint delivery and release cycles.
  • Identify technical risks, dependencies, and blockers early.
  • Use AI-assisted development tools responsibly to improve productivity while maintaining code quality and understanding.

About You

You are passionate about advancing the energy transition and building performant, accessible frontend applications for data-heavy B2B products. You bring a proactive, problem-solving mindset, strong attention to detail, and enjoy working in a small, ambitious team where engineers have autonomy and can make a meaningful impact.

We value ownership, accountability, a bias to action, and have a culture of feedback. As such, you should be a high-agency individual with self-awareness who wants TransitionZero to win. In addition to seeking out people with a proactive, problem-solving attitude and an eye for detail, as an evolving organisation, collegiality and empathy for our coworkers is a requisite.

As a growing tech startup operating in the climate space, the ground is always shifting beneath us. To be successful you need to have a high degree of adaptability and willingness to approach challenges with creativity and curiosity. Essentially you need to embrace change and be able to stay focussed on our long-term mission while delivering value incrementally, so we can build towards our future.

Skills & Experience

Essential

• 3+ years building production frontend applications with TypeScript and modern React.
• Experience building complex user interfaces, particularly data-heavy workflows involving tables, filtering, forms, and interactive visualisations.
• Understanding of frontend performance principles, including profiling, reducing unnecessary renders, and working efficiently with large datasets.
• Experience working with client-side data management patterns, including caching, synchronisation, invalidation, and optimistic updates (for example, TanStack Query or similar).
• Experience writing and maintaining frontend tests across different levels of the testing pyramid (for example, unit, component, integration, and end-to-end testing).
• Experience building accessible, reusable UI components using modern frontend approaches such as headless component libraries and utility-first CSS frameworks (for example, ShadCN, Base UI, or Tailwind).
• Ability to independently deliver well-scoped features, make appropriate technical decisions, and know when to seek input.
• Comfortable collaborating closely with product, design, and engineering teams in an agile environment.

Desirable

• Experience working in the energy sector, or building interfaces for modelling, simulation, or scientific data.
• Experience with data visualisation or grid libraries such as D3, AG Charts, or AG Grid.
• Familiarity with the wider TanStack ecosystem (Router, Table, Virtual, Form).
• Strong design sensibility and attention to UI/UX details.
• Experience applying generative AI tools or LLMs in practical engineering workflows.

About us

TransitionZero is a climate tech non-profit founded in 2021. TransitionZero builds software to reduce the time to build clean energy at scale. We pioneer open-access and open-source tools that make electricity system modelling more transparent, accessible, and actionable for governments, financiers and grid operators worldwide.

Our flagship tool, Scenario Builder, enables policymakers, planners and investors to rapidly build, analyse and share energy system and electricity grid models without coding expertise or external consultants. Supported by model-ready datasets, training and market insights, our tools strengthen in-house capacity and support resilient, affordable and locally-led energy transitions.