Staff Engineer (Global Billing, Payments & API)

Kaluza is an energy intelligence and optimisation software company that develops a vertically integrated platform designed to help energy providers manage and accelerate the transition to a cleaner, smarter energy system. The platform orchestrates billions of data points into a single, self-balancing network, enabling energy companies to streamline operations, enhance customer experience, and optimise energy flows in real time using data, AI, and automation. Kaluza serves leading energy providers across the UK, Australia, Europe, and Japan, and has been recognised as number one in the Frost & Sullivan Frost Radar Innovation Index 2025.

• Job title: Staff Engineer (Global Billing, Payments & API)
• Location: London / Bristol / Edinburgh (Hybrid Office - 3+ days per week)
• Salary: £97,000 - £122,000
• Team: Global Billing, Payments & API
• Level: TL2

This role is based in London, Bristol or Edinburgh and requires existing right to work in the UK.

At this time, we are not able to offer visa sponsorship for this role. We are committed to building a diverse, global team and our sponsorship policy is evaluated on a role-by-role basis. We encourage you to keep an eye on our careers site to stay informed about future opportunities where we are able to offer visa sponsorship.

Kaluza is the Energy Intelligence Platform, turning energy complexity into seamless coordination. We help energy companies overcome today’s challenges while accelerating the shift to a clean, electrified future.

Our platform orchestrates millions of real-time decisions across homes, devices, markets and grids. By combining predictive algorithms with human-centred design, Kaluza makes clean energy dependable, affordable and adaptive to everyday life.

With teams across Europe, North America, Asia and Australia, and a joint venture with Mitsubishi Corporation in Japan, we power leading companies including OVO, AGL and ENGIE, as well as innovators like Volvo and Volkswagen.

What will I be doing?

Kaluza runs the billing and payments engine behind some of the world's biggest energy retailers. This role builds and evolves the platform other engineering teams build on top of: the shared APIs, integration patterns, and technical standards that let billing and payments capability get built once and reused everywhere, instead of rebuilt separately for every new market or client relationship.

That matters because of where Kaluza is headed: as we grow into new markets and take on more of the world's largest energy retailers as clients, having a consistent, well-designed API platform is what lets new capability get adopted quickly and safely across every team that needs it, rather than each team solving integration and standards problems on its own. Getting this right directly shapes how fast Kaluza can extend billing and payments capability to new markets and clients.

We're also in the middle of reorganising how this part of the business works, moving toward one shared global core that every market configures rather than rebuilds. This role's remit, API platform and standards, is one of the technical foundations that shift depends on. Responsibilities include:

• You'll own system design and architecture for the API Platform and Standards squad, not just a single service.
• You'll create and challenge product and engineering proposals, backing design trade-offs with data.
• You'll diagnose and resolve complex technical and product issues, including in areas outside your immediate domain.
• You'll establish architectural patterns and technical standards that other teams build on top of.
• You'll take ambiguous, loosely-defined technical requirements and turn them into a concrete plan others can execute against.
• You'll influence engineering leadership, product, and adjacent squads to bring clarity and alignment on technical direction.
• You'll mentor and upskill engineers beyond your immediate team, contributing to a wider learning culture.

About You
Ideally you’ll have/be

• Have deep technical expertise applied to system design and architecture ownership across a squad, not just a single team or service.
• Be able to create and challenge product and engineering proposals and make design trade-offs, backed by data.
• Have a track record diagnosing and resolving complex technical and product issues, including in domains you aren't already close to.
• Be skilled at establishing and driving adoption of architectural patterns and technical standards that other teams build on top of.
• Be comfortable taking ambiguous, loosely-defined technical requirements and turning them into a concrete plan others can execute against.
• Be accomplished at influencing both upwards and outwards, bringing clarity and alignment to engineering leadership, product, and adjacent squads on technical direction.
• Have a track record mentoring and upskilling other engineers, and fostering a learning culture beyond your own immediate team.
• Be comfortable operating in a high-integrity data domain (billing or payments), where reliability, security, and auditability come before speed.
• Have demonstrable customer obsession and a working-backwards practice: start from the problem other engineering teams or end customers have, and design the simplest platform capability that solves it.
• Have a demonstrable record of applying AI/LLMs to deliver customer impact, not just adopting AI tooling internally.

What will set you apart 

• Direct experience with API gateway, versioning, or developer-experience standards work at scale.
• Direct experience in billing, payments, or financial-services domains.
• Experience operating a "global core, configurable edge" or multi-market platform model (one engine, configuration at the edge, no client-specific forks of core logic).

Where you'll work
We offer flexible working, with an expectation of 3 days a week in the office. This gives us the best of both: real time together to collaborate and build relationships, with the flexibility to work in the way that suits you best the rest of the week.

Kaluza Values
Here at Kaluza we have five core values that guide us as a business: Play to win, Solve the real problem, Build trust every day, Own the outcome, Go further together.

Our Perks

• Pension Scheme
• Discretionary Bonus Scheme
• Private Medical Insurance + Virtual GP
• Life Assurance
• Access to Furthr - a Climate Action app
• Free Mortgage Advice and Eye Tests
• Perks at Work - access to thousands of retail discounts
• 5% Flex Fund - to spend on the benefits you want most
• 26 days holiday
• Progressive Leave Policy - With no qualifying service periods, including 26 weeks full pay if you have a new addition to your family
• Personal Learning Budget - Upskill, learn and grow!
• Home Office Budget
  And more!

We want the best people

We’re keen to meet people from all walks of life — our view is that the more inclusive we are, the better our work will be. We want to build teams which represent a variety of experiences, perspectives and skills, and we recognise talent on the basis of merit and potential.

We understand some people may not apply for jobs unless they tick every box. But if you're excited about joining us and think you have some of what we're looking for, even if you're not 100% sure, we'd still love to hear from you.

Find out more about working in Kaluza on our careers page and LinkedIn.