iRobot Roomba S9+ review: the best robot vac for suction power and efficiency

iRobot's flagship Roomba S9+ is still one of the most efficient robot vacs money can buy

T3 Platinum Award
best robot vacuum cleaners
(Image credit: iRobot)
T3 Verdict

iRobot’s flagship S9+ is one of the very best robot vac combos you can buy. Its wide rollers clean up more stuff in a single sweep, its Clean Base holds about a month’s worth of carpet crap, its battery lasts for ages, it produces more suction than a toilet plunger and it’s excellent at mapping a home. Yes it’s expensive and yes it occasionally snags on rugs, but if you have a grubby home with animals roaming around, the S9+ is probably the best robot vac for your needs.

Reasons to buy
  • +

    It empties itself

  • +

    Superb navigation skills

  • +

    Brilliant on carpet

  • +

    Wide roller head

  • +

    Ace battery life

  • +

    Class A suction

Reasons to avoid
  • -

    Doesn't like some rugs

  • -

    Expensive

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iRobot’s Roomba S9+ has been around for some time now but, having recently reviewed its new stablemate, the iRobot Roomba J7+, we thought you’d like to know why we think the older – and more expensive – S9+ is still the best robot vac in Roomba’s ever expanding arsenal, especially if you have a lot of carpets – and pets. 

However, before we start, I should inform you that any iRobot Roomba model that comes with a ‘+’ moniker means it ships with a Clean Base auto-bin emptying system. If you opt for a model without a ‘plus’ attached, you will pay a few hundred pounds less but you will also need to chase the robot around the house to empty its tiny onboard bin yourself. I guarantee you will tire of this bot-chasing malarky just 30 minutes after setting it off for the first time and wish you’d spent a bit more and bought the ‘plus’ version instead. If you have a few hairy pets in the household – especially long haired cats, German Shepherds or Golden Retrievers – you can safely expect to be emptying the robot’s internal bin about every ten minutes. The moral here is to always figure in the extra cost of a self-cleaning station no matter what brand of robot vac you’re considering.

With that cautionary tale out of the way, let’s see what’s so special about the S9+ and why it’s still the best robovac in the iRobot Roomba range.

Where can I buy an iRobot Roomba S9+?

Brits have a wide choice of online emporiums from which to buy the iRobot Roomba S9+. If you prefer to buy direct from the manufacturer, consider the iRobot store (opens in new tab) where it retails at £1,499 and 99 pennies. Alternatively, the S9+ is available from Amazon (opens in new tab) for the same price or £62.50 for 24 months with 0% APR.

If living Stateside, try Amazon (opens in new tab) where the S9+ retails at just $879 – a steal – or Walmart (opens in new tab) where it retails at $1,099. And if residing Down Under, try the iRobot store where it’s selling at a considerably higher price of A$2,899. That’s about £2,075 in US dollars. Ouch!

iRobot Roomba S9+ review

(Image credit: iRobot)

iRobot Roomba j7+ review: design

As the ‘+’ moniker suggests, the S9+ ships with the excellent iRobot Roomba Clean Base. The Clean Base is basically a charging station that also automatically empties the contents of the S9’s small bin into a large dust bag that you throw away after a month or so. In essence, whenever the S9 detects it’s bin is full – even mid clean – it will trundle back to dock where the detritus in the S9’s mini bin is sucked into the larger bin bag using a powerful vacuum.

At 48cm in height, the S9+’s Clean Base is much taller than the J7’s so it’s not quite as elegant when it situ. However, the sound volume of the Clean Base’s emptying sequence is much easier on the ear than the racket its stablemate the J7+ makes, so that’s a major plus right from the off.

iRobot Roomba S9+ review

(Image credit: iRobot)

Another major advantage of the S9 is its shape. Where most robovacs are circular with a small 16cm roller section that straddles the midriff, the S9 is D shaped and its long 23cm twin rubber rollers are positioned near the front, almost across the entire width of the machine. This means that the S9 is not only better at collecting dust along edges, it also picks up more detritus with every sweep. Moreover, the slower spinning side bristle doesn’t seem to fling hard floor matter around as much as some other models. As it turns out, iRobot’s rubber rollers do a grand job of beating deep down into carpet pile. However they can sometimes clatter across hard flooring, but thankfully not in an irritating way.

The S9’s battery is extremely powerful (3,300mAh vs 1,800 mAh) which means it can run for up to a phenomenal 120 minutes at a time and that makes it a perfect choice for large homes. It also comes with an anti-allergen system for those with household pets.

The S9’s suction is much more powerful than any other Roomba on the market and probably the majority of its competitors. At 2,200 Pascals, this vac has some serious suction and that means it's a top choice for carpets where it really excels. It even automatically detects the floor surface and ramps up or lowers the suction accordingly.

iRobot Roomba S9+ review: mapping and app features

iRobot Roomba S9+ review

(Image credit: iRobot)

When it comes to room mapping, the S9 is master of the floorspace. Its Advanced vSLAM + Imprint Smart Mapping technology is rock solid and able to navigate under beds and sofas even if there’s a valance over the edge. However, as is the case with all robovacs, you must leave it to its own devices, no matter how random its vacuuming pattern may seem. After about day two or three it will have accurately mapped your entire floorspace which you can then customise in the excellent iRobot app (iOS and Android).

For instance, if you have an open plan environment which the robot normally covers in a single sweep, you can divide the area into separate zones and command it to just clean a specific area like, say, the living room or the kitchen. And if there are areas you’d rather the bot avoided completely – like coconut fibre doormats, around the pet’s water bowl, etc – you can easily create no-go zones by using the app’s pinch and zoom facility. The app also provides the wherewithal to create a wide variety of cleaning schedules for different rooms at different times.

iRobot Roomba S9+ review: initial set up

In our test, the s9+’s initial wi-fi setup was an absolute breeze – indeed, it’s one of the few robot vacs to happily sync with a 5GHz network, a major plus for anyone with a MESH-style system that can confuse many 2.4Ghz devices. To set it up, simply follow instructions in the app and it’ll be up and running in no time.

iRobot Roomba S9+ review: performance

iRobot Roomba S9+ review

Unlike robot vacs that use LiDAR, the Roomba S9's sensor and camera system allows it to venture under beds and sofas with valances

(Image credit: iRobot)

When it comes to performance, the S9 excels in most disciplines, especially on thin to medium-pile carpet. Granted, it’s not that great at making any headway on really deep pile carpet, but then I haven’t found any robot vac that can handle the ultra deep-pile carpet I inherited when I moved in.

Rugs, however, are this vac’s arch nemesis, especially thin ones with tasseled edges. This is because the rollers are positioned lower than almost any other robot vac I’ve ever used. Low rollers are brilliant for hard floors and medium pile carpet but they do have a tendency to snatch the edges of rugs on a regular basis.

However, this bot isn’t stupid so it will always switch the rollers off when it detects a possible roller jam and slowly work its way over the ruffled edge before switching the rollers back on again. In most instances the system works remarkably well but I can’t safely leave the S9 to reliably vacuum the house while I’m out unless I lift up most of the rugs. It’s a bind, I know, but I’ve kind of got used to it. And besides, this vac does everything else so amazingly well that I’m inclined to overlook the occasional rug ruffling issue.

iRobot Roomba S9+ review

The iRobot S9+ works in tandem with iRobot's Braava Jet M6 robomop

(Image credit: iRobot)

The S9+ also works in tandem with iRobot’s Braava Jet M6 mopping bot which you can read about in our full length review. In essence, once the S9 has completed its vacuuming task, it sends a message to the Braava to start mopping. You can buy the S9+ and the Braava Jet M6 as a bundle (opens in new tab) for a pricey £2,200.

iRobot Roomba S9+ review: verdict

iRobot Roomba S9+ review

(Image credit: iRobot)

If you have a large home where hairy pets reside, the S9+ is a no brainer. Aside from some rug issues, it performs superbly well on hard floors and is certainly more efficient on carpet than many other robot vacs on the market. But if cost is a barrier – and let’s face it, this bot ain’t cheap – the lower priced J7+ will perform the same set of tasks almost as well.

iRobot Roomba S9+ review: also consider

Looking for a cheaper alternative? Try the new iRobot Roomba J7+ (opens in new tab) which avoids all kinds of obstacles on its own, including doggy poo. Or maybe the excellent Roborock S7 (opens in new tab) hybrid vac and mop in one, which we conveniently review in full right here.

Derek (aka Delbert, Delvis, Delphinium, Delboy etc) specialises in home and outdoor wares, from coffee machines, white appliances and vacs to drones, garden gear and BBQs. He has been writing for more years than anyone can remember, starting at the legendary Time Out magazine – the original, London version – on a typewriter! He now writes for T3 between playing drums with his bandmates in Red Box (redboxmusic).