About 17 months ago at CES 2015, we got our first look at a prototype of Stack Lighting's Nest-compatible, sensor-equipped smart bulb, known at the time as the Alba LED. Since then, Stack has ditched the "Alba" moniker (it's just the Stack Downlight now, with A-shaped "Stack Classic LEDs" on the way this September). The price of a two-bulb starter kit is lower now, too, down from $150 to $99, with additional bulbs selling for $45 a piece.
That makes Stack more affordable than both Lifx and Philips Hue -- and I'd argue that Stack's bulbs are smarter than both. No, they won't change colors, but they will change color temperatures, offering a yellowy 2,700 K, a bluish-white 6,500 K, or anything in between. Put the bulbs into "Auto Mode," and they'll automatically adjust their own brightness and tone throughout the day using built-in ambient light sensors. There's also a presence sensor in each bulb -- if they see you walking into a room, the lights will fade on automatically to light your way.
There's really not much to dislike about these bulbs. They offer a good mix of features that all work as promised, with app controls that do an admirable job of hitting the sweet spot between comprehensive and easy-to-use. What's more, they'll work with your Nest thermostat, cleverly telling it to crank the heat a little higher if they spot you in a room that tends to stay colder than the rest of the house. You can also automate the bulbs on IFTTT, which lets you sync them up with a wide variety of other popular smart home services and gadgets, including Amazon's Alexa. At $45 a piece, Stack's bulbs aren't cheap, but they still make one of the strongest cases for smart lighting we've seen to date.
Getting started with Stack is pretty simple -- just download the app and plug in the hub (it's yet another hunk of white plastic, but hey, at least it's hexagonal). From there, the app will ask you to name each room where you'll be installing smart lights. Once you do, you'll add bulbs to each one.
And that's how the app keeps things organized: by room. That applies to the controls, too. Instead of controlling individual bulbs, you control an entire room's worth of bulbs at the same time. I'm not a fan of this blanket approach -- there are definitely times when you want to be able to turn one light on in a room without turning all of the lights on. Of course, you could list each individual bulb as its own "room" as a workaround, but that's a pretty clunky solution.
Once you've gotten your lights organized, you can dial the brightness and color temperature of each room up and down or assign them to one of three color temperature presets. There's also an Auto mode that will let each bulb adjust its own brightness and color temperature settings throughout the day based on the time and the ambient light conditions in the room.
By default, the lights will automatically turn on when they detect motion, then automatically turn off after motion is stopped. If you want, you can tell certain rooms to stay lit for longer after motion stops, or just disable the auto-off feature altogether.
You'll find a similar depth of control with the rest of Stack's features. An alarm feature lets you set the lights to wake you up at a certain time each morning -- you can customize things like the quality of light, the range of brightness and the amount of time it'll take to fade to full blast. In the app's scheduling mode, you can program the lights to behave in different ways at different times of the day. Put the app into sleep mode, and any bathroom or hallway lights will switch into a fully customizable nightlight setting when they detect motion.
The controls aren't perfect, though. I couldn't find a way to set that sleep mode to run automatically each night, for instance, or a way to trigger it from outside of the app. And manually adjusting each room's lighting felt sluggish to the touch, with narrow, over-sensitive sliders that make it tough to hit precise settings.