SplitGrid is a bill-splitting app for flatmates that charges each person based on their actual energy usage — not a flat equal split. I designed the full experience from onboarding to settlement.
Anyone who has lived with roommates knows the feeling. You go to bed at 10pm, use one lamp, and charge a single phone. Your flatmate runs a gaming PC, charges an electric car overnight, and leaves every light on. At the end of the month, you split the bill equally and silently resent each other.
SplitGrid solves this by connecting to smart home devices, tracking actual energy usage per person, and calculating each flatmate's real share of the bill. The result is a fairer system — and far fewer awkward conversations.
"The core design challenge wasn't the data — it was making complex energy tracking feel simple, transparent, and fair to people who just want to pay their bills and move on."
When bills are split equally regardless of usage, heavy users are subsidised by light users. This creates resentment and conflict in shared living spaces.
Flatmates have no way of knowing how much energy each person or device is actually consuming — making fair conversations impossible.
Chasing flatmates for money, remembering who owes what, and managing multiple transfers every month is time-consuming and awkward.
Before jumping into design, I explored the shared living landscape to understand what actually causes friction between flatmates around bills. The findings reframed the problem entirely — this wasn't a maths problem, it was a trust and transparency problem.
Flatmates rarely confront each other about unfair usage. Instead, frustration accumulates over months — equal splits feel deeply unfair when one person owns an EV or runs high-power appliances.
When people can see exactly how much their devices cost in real time, they naturally reduce unnecessary usage. Transparency is both a fairness tool and an energy-saving one.
Flatmates won't accept a new billing system unless they can verify the numbers themselves. Any design that hides the calculation logic will be rejected — even if the result is correct.
Existing smart home apps require complex manual device configuration. For SplitGrid to work, adding a device had to feel as easy as scanning a QR code — because it does.
"Fair billing only works if every flatmate trusts the system. That meant designing for transparency at every step — not just accuracy."
Every screen that involves money needs to show how the number was calculated. This led to the per-device watt/cost breakdowns in the All Devices screen and the room-by-room distribution on the dashboard.
The radial device map came directly from the insight that ownership needs to feel personal. A list of device names doesn't create a sense of "these are my devices and this is my footprint" — a spatial, person-centred view does.
Supporting Matter protocol QR onboarding was a direct response to the finding that setup friction kills adoption. If connecting a device takes more than 30 seconds, users give up.
The app needed to guide users through a journey that starts with zero data — no devices connected, no flatmates added — and ends with a fully automated, fair billing system. Each screen was designed to make that journey feel effortless.
The 3-screen onboarding uses clear value props ("Pay for what you use", "Control your appliances") before asking users to set up anything. This reduces drop-off by making the payoff clear upfront.
The Setup screen offers both a smart building search and a manual device entry option. QR scanning via the camera makes adding smart devices (Matter protocol) feel instant and modern.
Showing that existing contacts already use SplitGrid creates immediate trust and lowers the friction of inviting flatmates to join.
The home screen surfaces energy score, energy distribution by room, shared expenses, flatmate payment status, and a payment record chart — all in a single scroll. Grouping related information into cards prevents cognitive overload.
Instead of a flat list, devices are shown in a radial orbit around the user's profile. This makes the concept of "your" energy footprint feel personal and spatial.
Each flatmate's device list is expandable with watt/cost breakdowns and colour-coded usage indicators. This screen is the key to making fair billing feel trustworthy.
A donut chart showing the $280 total split across flatmates, combined with a one-tap transfer row and transaction history, makes the final step feel simple and final.
Instead of a flat list, devices orbit the user's profile in a radar-style layout. This makes energy ownership feel personal and spatial — immediately answering "which devices are mine?"
Supporting the Matter smart home protocol means users can scan a QR code to instantly add any compatible device. This reduces setup friction to seconds rather than minutes.
A single "Energy Score" number on the home screen gives users an immediate sense of their usage without needing to read charts — designed for the 3-second glance.
Green, yellow, and red dots on each device in the All Devices screen let users instantly identify high-consumption appliances without reading any numbers.
SplitGrid sits at an interesting intersection: financial transparency, smart home technology, and interpersonal relationships. Designing for all three at once meant that every decision had social consequences — not just usability ones.
The most important insight was that fairness needs to be visible, not just accurate. It's not enough that the system calculates the right numbers — users need to be able to see exactly how those numbers were reached.
Every design decision around data visibility was motivated by the same goal: if a flatmate questions a bill, the answer should be one tap away.
The app handles complex IoT data. The design challenge was revealing that complexity only when users needed it — keeping the daily experience simple.
This isn't just a utility app — it mediates relationships between people. Every screen that shows another person's data required careful thought about privacy and framing.
Notification design for payment reminders, dispute resolution flows, and an AI-driven suggestion engine for reducing energy costs.