Universal UI for Carrier Smart Thermostats

Hardware and mobile application interface design system for Wi-Fi connected thermostats from the world’s leading HVAC company

The First Iteration

Beginning in 2015, the UX team at GS&F designed the mobile application and hardware UI for Carrier's budget smart thermostat models, the Côr 5C and 7C. Over the course of two years, we continuously designed out additional features, ran experiments to validate new feature concepts, and worked with Carrier's offshore development team to execute those designs.

A selection from the hundreds of screens we developed for the 5C / 7C application in 2016. I acted as the primary designer on this iteration of the app, reconciling the work of several previous designers into a unified design approach.
A fractured brand experience

Through the course of working on the Côr 5C and 7C thermostats, we discovered that the user experience and aesthetic for the full Côr line of products was badly disjointed. Not only did the user interface completely differ between models, but in almost all cases the mobile application and hardware interfaces shared few similarities as well. For a brand struggling to assert itself in a market created by Nest, the lack of consistency and poor user experience (in addition to other factors) were hindering Carrier's ability to compete.

The full line of Carrier thermostats and associated applications, mostly as they appeared in 2016, with inconsistency issues clearly apparent.
Establishing the Universal UI Design System

Seeing this weakness, we recommended that the product team allow us to establish a design system that could scale across devices and up and down models with varying feature sets. It would have to be extremely flexible, visually restrained enough to work on limited hardware, and yet also elevate the brand. Although we considered and tested numerous different aesthetic directions, users showed a strong preference for a simple, dark user interface that was well organized and easy to read. We carried forward one of the key learnings from our work on the Côr 5C / 7C app—that users responded well to a plainly written sentence that clearly explained their system status, upfront on the home screen at all times.

With the leading direction established and the institutional knowledge developed from working on Côr 5C/7C, our senior UI designer fleshed out the full design system and collaborated with engineers, business leaders, and marketers to satisfy all the technical requirements of all the thermostat models available in the Côr line. Each complex feature of the application or hardware—scheduling, unit configuration, etc. —was designed, tested, and redesigned to ensure the most functional solution possible.

Flexibility and extensibility

Even as the business and engineering teams introduced new features, the system held up remarkably well and required few new patterns in order to satisfy unforeseen feature requests. Because the system was well considered and documented, the business and UX teams were able to satisfy new mockup requests simply through collaborative conversations.


As the culmination of nearly four years of research, design, prototyping, testing, conference calls, and QA work, the completion of Universal UI was the pinnacle of our UX and visual work for Carrier. We believe that with stable engineering behind the system, it would have repositioned the Carrier line of smart thermostats to compete in the consumer-facing market.