This Is the Best Robot Vacuum I’ve Tested, and It’s 40% Off on Prime Day

Prime Day 2025 runs from Tuesday, July 8 through Friday, July 11, and Lifehacker is sharing the best sales based on product reviews, comparisons, and price tracking tools.

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New to Prime Day? We’ve got the lowdown on everything you need to know . Sales are accurate at the time of publication, but prices and inventory are always subject to change.

Robot vacuums tend to work best in homes that don’t have a lot of clutter: no cords, large open spaces, not a lot of stuff on the floor. The sweet spot for robot vacuums is dust or some simple dirt. But that’s not what most people have in their homes: They have pets. They have kids. They have small houses filled with stuff. Most people buy a robot vacuum in the vain hope that it will just take care of the floor, without any help. Most robots get stuck in all that clutter, and you’ll spend all your time unclogging them or rescuing them from where they’re stuck — and you’ll still have to keep a broom and mop nearby and supplement the robot’s work. The 3i S10 Ultra is different.

The best part about the 3i is that you never have to change the water because it can do it for you. It boils the water when the robot returns to the dock, and the resulting distilled water is disinfected and ready to use. If the robot runs out of water, it does it itself with a built-in dehumidifier. I never had to change the water.

But as convenient as that is, it wouldn’t mean anything if the robot couldn’t clean. The 3i S10 was the first robot I’ve ever tested that could vacuum large chunks of mulch and pet toys off the floor without rattling or clogging the vacuum. The tower then pumped the vacuum away when it was docked. The 3i has two large scrapers at the front of the robot that spin in opposite directions, pushing the debris toward the rollers. One roller is amazingly effective at pushing that debris off the floor and into the vacuum, where 13,000 Pa of suction sucks it all up. That’s not even a lot of suction for today’s premium robots, but it works here. It’s also quiet. Blessedly quiet.

Then out comes the mop. This is the roller mop I like best, and it did a good job, even on the first try. The robot’s navigation was also efficient, navigating cords and the maze of paws and dog toys under my couches without issue. It didn’t get stuck in piles of laundry, it avoided them. It knew what was a dog toy to avoid, and what was a dog toy to vacuum into oblivion.

Here are a few caveats: First, the tower weighs a ton—about 50 pounds. You won’t want to move it once it’s installed. Also, the robot itself is tall—over four inches—and the mop doesn’t use hot water, only regular distilled water. Also, 3i is a new company, so that might be a concern. For me, none of these issues were noticeable or affected the result, which was a clean floor.

There are smaller vacuums on sale this week that are still more expensive than the 3i S10. For example, I’d recommend it over the Saros 10 , 10R , or Dreame X50 , which I like and are considered premium robot vacuums. The 3i S10 is normally $1,899.99, but it’s currently on sale for $1,199.99 ($1,139.99 if you use the additional coupon code S10USAVE5 at checkout). Yes, it’s still pricey, but at this sale price, it may be worth the extra cash.

Looking for something else? Retailers like Walmart, Best Buy, and Home Depot are running Prime Day sales that are especially helpful if you don’t have Amazon Prime.

• Walmart’s Prime Day sale starts at midnight on July 8 and includes discounts of up to 50% . It’s an especially good option if you have Walmart+.

• Best Buy’s Prime Day sale , “Black Friday in July,” runs through Sunday, July 13, and offers some of the best tech sales online . It’s an especially good option if you’re a My Best Buy “Plus” or “Total” member.

• Home Depot has extended its July 4 sale through at least July 9, competing with some of its own great deals . It’s a particularly good option if you’re looking for power tools, appliances, or outdoor gear.

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