How to Make a Hot Thermostat App

The increased adoption of smart thermostats promises more convenient and energy-efficient homes. Conventional programmable thermostats reduce energy use by 30%. Smart thermostats promise additional savings on energy bills. But that requires users to be able to fully navigate their thermostat and the app that they use to control it in order to take advantage of the additional energy saving features.

1. Scheduling is a key feature.

One of the top reasons users purchase smart thermostats is to save energy. People want to be able to adjust the temperature based on the weather or to control their thermostat while away from home. The best way to save energy, however, is to automatically turn down the heater or A/C when people leave the home.

While geofencing is a popular energy-saving feature, poor geofencing performance is also a very common topic among the app store reviews for HVAC apps. In practice, it’s difficult to get geofencing to work smoothly, particularly for a multi-user household. So in reality, most energy saving will come from well-defined thermostat schedules. While it’s important to make the geofencing feature prominent and easy to use, it’s critical to make sure scheduling is discoverable and easy to use.

Schedules are often difficult to find as they’re frequently hidden in the app’s settings, which are not part of the natural user journey. They can also be so tedious to set up that homeowners will rely on their HVAC installers to do it for them. While installers can handle some of the configuration, it’s important that users learn how to adjust schedules to fit with their ever-changing lives. Took a day off and want to sleep in? Got a new baby that turned your days into 3-hour increments? Users can’t be expected to call their installer every time their life circumstances change. They need to learn how to use schedules through progressive disclosure.

The app should provide a few preconfigured schedules that refer to common events like waking up, going to and returning from work, and going to bed. Once users have tried a schedule, they can customize it based on things like their unique wake-up time and preferred temperature. This gradual learning by experiencing and learning by doing helps users take advantage of the powerful energy saving features that incentivized them to buy a smart thermostat in the first place.

By their nature, schedules are a set-it-and-forget type of feature. Users will interact with them less frequently than changing the temperature on their thermostat. This means that they don’t belong on the home screen, where they would clutter the view every time a user tries to adjust his or her thermostat. At the same time, they need to be easily discoverable in the app's primary navigation.

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2. Intuitive navigation

Surprisingly, many smart thermostat apps lack a tab bar for navigating between screens. A tab bar helps users instantly build up a mental model of the app. It’s important that the tab bar is persistent across the app and highlights the tab that corresponds to the currently opened screen. Otherwise, users have to tap around to find features every time they open the app.

3. Familiar interactions.

Unlike a social media or a gaming app, a smart home app is not used many hours per day. As a result, users don’t have time to figure out a unique layout. To help them navigate easily, the app should leverage what they’ve already learned from using other common apps.

People have developed intuition for how to interact with their mobile devices while using other apps. Apps can leverage that intuition by keeping common features in familiar places and using common icons and colors. Apps should also have information at the top of the screen, since people tend to scan screen top-to-bottom, and controls on the bottom half, where the thumb naturally falls.

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A user’s expectations will also change, depending on whether they are using an iPhone or an Android phone. The app should closely follow Apple’s Human Interface Guidelines and Google’s Material Design guidelines.

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4. Replicate the physical world.

Modern thermostats were invented over 130 years ago and have carried forward many common interfaces that have become intuitive to users. The app should model familiar UI from the physical world, like the buttons and toggles that people use every day. Don’t introduce controls that users have never seen in a home or wouldn’t know how to interact with physically.

The same thing goes for colors and symbols that are commonly understood offline. Everyone knows that red means hot and blue means cool, so that’s not a good opportunity for a bold redesign!

5. Core features on the home screen.

When digitizing controls that would otherwise be easily accessed on a hallway wall, the app needs to make it just as quick for users to access those features. Users need to be able to set the temperature or turn off the thermostat from the home screen. These controls should be the most prominent. As one App Store review of the Ecobee app notes:

Who in the world has two homes in which they need to control the temperature? The latest update forces each user to now add more clicks to get to the main page just to adjust the temperature.

The human brain can only handle around 7 items at once. Don’t include features that aren’t needed, and don’t fill the home screen with features that will rarely be used. Instead, make sure the most important features are easily accessible and intuitive to use.

Highlighting select features on the home screen and moving less frequently used features to subsequent screens also help users learn how to use the app in an intuitive way. Users don’t have the patience or bandwidth to learn everything all at once, which is why they tend to quickly tap through tutorials and rarely tap on information symbols.

6. Obvious controls that instantly communicate state

Users should instantly know how to adjust the temperature by looking at the home screen. If they need to poke around in the app or watch a tutorial, the control isn’t clear enough. Ideally, they should know how to interact with the control before touching the screen, i.e. whether it requires a tap, press, swipe, or drag. The control should also communicate the state, e.g. the current temperature settings and whether the mode is set to cool, heat, or auto.

7. Self-sufficient hardware for core features.

It’s great if you can make it super simple to access the core features in the app. But you shouldn’t always force users to use the thermostat app, especially for basic interactions.

Sometimes a user is standing next to the physical thermostat and doesn’t have their phone handy. Other times, people in the home may not be users of the app at all. Imagine staying with friends or family only to discover that the futuristic thermostat on the wall won’t allow you to cool down a sweltering room without being added as an authorized user.

Making the core functionality inaccessible without the app is a sure way to frustrate users enough to write negative app store reviews and tell their friends to avoid purchasing the same system they did.

8. Consistently labelled numbers and icons

Given how briefly and infrequently people use smart home apps, they never have time to learn what the unlabeled icons or different numbers in the app represent. When there’s any potential for ambiguity, numbers and icons should be labelled so that users know what they’re looking at, whether they’re opening the app for the first time, or just for the first time this week. For example, does “74°” on the screen mean it’s 74° in the user’s home? Or that the A/C is cooling the room to 74°? Or even that it’s 74° outside? User’s shouldn’t have to guess the answer, nor should they have to look in an owner’s manual.

9. Visually represent complex concepts and avoid jargon.

Thermostats, by their nature, involve many more complex concepts than other home appliances. To take full advantage of a smart thermostat, a user needs to understand concepts like setpoints, modes, and schedules. As much as possible, these abstract concepts should be communicated with visuals so that the user isn’t confused by new terminology.

Thermostat apps tend to have a surprising amount of industry jargon that’s often confusing to users. Terms like “faults”, “setpoints”, “zones”, and “holds” are commonplace in the HVAC industry, but they’re not instantly recognizable to most homeowners. Try to avoid jargon and label features in a way that new users can understand.

10. Actionable error messages.

Error messages can be a helpful tool when a user needs help. But they also signal to the user that something in the app isn’t working. To avoid making the app feel broken, messages should only be used when they are really actionable. They should always clearly state what’s wrong and the action the user needs to take (e.g. “please check your internet connection”). If the action doesn’t technically require the users’ participation (e.g. “try again”), it often makes sense to retry on behalf of the user rather than overloading them with error messages.The increased adoption of smart thermostat promises more convenient and energy efficient homes. Conventional programmable thermostats reduce energy use by 30%. Smart thermostats promise additional savings on energy bills. But that requires users to be able to fully navigate their thermostat and the app that they use to control it in order to take advantage of the additional energy saving features.

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