Sleep Number i8 Smart Bed review: Our sleep expert's go-to for custom comfort, sleep-tracking, and couples

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As Business Insider's mattress reviewer, I don't get to sleep on the same bed every night. But if I could stick with one bed, I would choose a Sleep Number. Thanks to its high-end service and innovation, Sleep Number is the top name in adjustable air mattresses. This is evident in the i8 mattress, the top adjustable bed pick in our best mattress guide. 

All Sleep Number beds have 20 mattress firmness options that can be customized on each side of the bed. The i8 innovates on this with the sleep-tracking Sleep Number app and responsive air that adjusts the firmness for consistent comfort as you shift in the night. This feature might sound gimmicky, but it helps me stay asleep.

Setup

Sleep Number provides in-home set-up with its own delivery crew, which is included with the mattress purchase. I like that they don't rely on third parties for this service because you know you're getting people who know what they're doing. 

This proved true when the delivery people couldn't get the queen bed frame up my tight staircase. They recommended a split king frame, which comes in two pieces. This pushed the delivery date back a month. If you're unsure about what bed size you need, check out our mattress size chart.

The second try was successful. The workers set up the base and mattress in about 45 minutes, ensuring my phone was paired with the bed and showing me how to use the app. Despite the brutal task of carrying the components to my third-floor bedroom, they were professional and helpful. 

Though the bed had a strong new bed smell, the odor dissipated by bedtime.

Review of the Sleep Number i8 Smart Bed

I'm a side sleeper but spend time in every sleeping position. Using the Sleep Number app (available for iOS and Android), you can turn on the "responsive air" function, which automatically adjusts the firmness as you change positions. This gives you consistent comfort and pressure relief. It worked seamlessly and did a good job of facilitating restful, undisturbed sleep.

The Sleep Number i8 Smart Bed uses ballistocardiography, a measure of ballistic forces coming from your heart, to calculate your sleep quality and provide a sleep score. After you track your sleep for several weeks and input your sleep goals, the app offers tips for more productive sleep. 

In the six months my wife and I tested the bed, Sleep Number made several tweaks to the app that have improved the sleep-tracking accuracy. I checked for accuracy by comparing the data to my Garmin Forerunner 945 smartwatch readings and my subjective experience.

Sleep Number is best known for its adjustable firmness. The mattress has 20 firmness levels, and your "sleep number" is your preferred firmness level from 5 (softest) to 100 (firmest). My sleep number was 35, but my wife preferred 55. Fortunately, the two sides are individually adjustable, so couples with vastly different preferences can be comfortable. 

Finding the right firmness was easy. Sleep Number recommends lying in your preferred sleep position and starting at 100. Then, using the app, slowly decrease the firmness until you're comfortable. Finding my sweet spot took me a few nights of trial and error, but I didn't make additional adjustments.

I was impressed with the mattress's edge support. I felt comfortable sitting on the side of the bed to put on my socks and shoes and lying on the edge to cuddle my wife in the morning.

I love how few wires the i8 smart bed has. The adjustable base (I tested the FlexFit 2) and mattress are powered by one electrical cord that plugs into your wall. This starkly contrasts with the other adjustable beds I've tested, which leave several wires on the floor and require multiple wall outlets. 

I also appreciated that I didn't need a remote to operate the mattress. The app controls everything, and it was whisper-quiet when I made adjustments.

Cons to consider

The motion isolation of the Sleep Number i8 was subpar. My wife said it felt like a waterbed when I flopped on the mattress. 

The heat dissipation was also poor. When I got up to go to the bathroom at night, the spot where I was sleeping would still be warm when I returned. Hot sleepers may want to consider another option. I'd recommend the Sleep Number Climate360 if you can afford the $10,000 price tag. I was impressed with its built-in heating and cooling capabilities, giving you a custom feel. It may be the best cooling mattress I've tested.

As I tested mattresses on the other side of our "bedsroom," my wife continued to sleep on the i8 for several months. She liked to sprawl out. Unfortunately, the divider between the two air chambers makes sprawling uncomfortable. Also, the sleep tracker didn't recognize when one person was sprawled across both sides of the bed. Consequently, her sleep stats were inaccurate when she did this. For these reasons, I would not recommend Sleep Number beds for people who sleep alone.

The mattress is also hard to move since it is attached to the base. You can try to detach it and move it separately or attempt to move the whole unit. Either way, it's a chore.

Should you buy it?

At $3,000 for the queen, the Sleep Number i8 is out of the price range of most consumers, even if it does come with in-home setup. But it's worth it if you can afford it, especially considering a 15-year warranty covers it. Sleep Number also offers financing options.

Your mattress preferences change over time. Two years ago, I was 50 pounds heavier and preferred a firmer mattress. Now, I look for something softer to keep my spine aligned as I sink in less. If this happens and you have a non-adjustable mattress, you either need a new mattress or a mattress topper (see our best mattress topper guide), or you can live with being uncomfortable. With a Sleep Number, you can just choose a new firmness. 

I recommend the Sleep Number to older couples since comfort preferences are more refined as you age. 

The bottom line

If I weren't a mattress tester trying out new beds every two weeks, I would sleep on a Sleep Number Smart Bed every night. Even though I sleep hot and the Sleep Number i8 tends to retain heat, I recommend it because of the responsive air feature that keeps my comfort consistent no matter my position. As a stats person, I like as much sleep tracking info as possible to achieve better, more restful sleep. I strongly recommend the Sleep Number i8 Smart Bed if you can afford it.