How to apply for Senior Mobile Engineer

About Fuse Energy

Fuse Energy is an energy startup building a fully integrated system: solar and battery generation, hardware, grid infrastructure, real-time power trading, and home installation. It has raised over $200M from investors including Balderton, Lakestar, Accel, Creandum, Lowercarbon, Ribbit, 20VC, Hummingbird, and Collaborative Fund. It sells directly to consumers to cut out the middleman and lower costs.

About the role

This is a senior mobile engineer role on a small, high-ownership team. You will own features end to end, from customer-facing product to internal tools, and ship consumer-facing AI features into production on mobile. You will work in Swift and Kotlin across iOS and Android alongside mobile and web engineers.

A typical day

You might build or refine Swift and Kotlin components that AI composes into per-customer experiences, then test how those components behave under different AI outputs. You could also work on internal tools, coordinate with backend and web engineers, and ship a consumer-facing AI feature to production. The details of team rituals and release cadence are not stated, so ask about them in the interview.

Who Fuse Energy is looking for

• Strong production experience in both Swift and Kotlin, with shipped apps on iOS and Android.
• Comfortable owning features end to end without fully-specced tickets, from product decisions to release.
• Has shipped consumer-facing AI features into production on mobile, or worked closely with AI-driven UI systems.
• Builds reusable UI components that can be composed dynamically, since AI composes a different experience for each customer from those components.
• Brings a high bar of craft and ownership to match an already strong backend and infrastructure team.

Tips for this application

• Show shipped apps in Swift and Kotlin. Link to App Store and Play Store listings you personally contributed to.
• Describe one feature you owned end to end. State the problem, what you decided, what you built, and the result.
• If you have shipped AI features on mobile, detail the architecture: how the AI output reached the UI, latency handling, and fallbacks.
• Mention how you build reusable UI components, since the role explicitly builds components that AI composes into per-customer experiences.
• Reference Fuse Energy's specific model: own solar and batteries, hardware, grid, real-time trading, AI across the business, and direct-to-consumer sales. Connect your mobile work to that model.

What to cover in your cover letter

Ownership without fully-specced tickets: give an example where you defined the work yourself. Dual-platform ability in Swift and Kotlin, not one platform plus willingness to learn the other. Shipping consumer-facing AI features into production on mobile. Building composable UI components that support dynamic, per-customer experiences.

Research before applying

• Fuse Energy's funding history and investors, including Balderton, Lakestar, Accel, Creandum, Lowercarbon, Ribbit, 20VC, Hummingbird, and Collaborative Fund.
• What Fuse Energy means by a fully integrated energy company: generation, hardware, grid, trading, AI, and home installation.
• Fuse Energy's consumer product and mobile app. Note current features and where AI could change the experience.
• The UK energy market and what direct-to-consumer selling changes for pricing and customer experience.

Likely interview topics

Based on the job description, expect questions about:

• Walk through a feature you owned end to end. How did you scope it without a full spec?
• How have you shipped an AI-driven or dynamic feature on mobile? How did you handle latency, errors, and fallbacks?
• How do you design UI components that can be composed differently per user?
• Compare your Swift and Kotlin work. Where are you stronger, and how do you keep both current?
• How do you work with backend and web engineers when the backend and infrastructure are already strong?

Common mistakes to avoid

• Applying with experience in only Swift or only Kotlin. The role requires both across iOS and Android.
• Describing only ticket-based work. The role explicitly is not fully-specced tickets.
• Claiming AI experience without a shipped mobile example. The role requires shipping consumer-facing AI features into production.
• Generic cover letters that do not mention Fuse Energy's integrated model or its direct-to-consumer approach.