The Little Green is the best-selling portable carpet cleaner in America and one of the least specified machines we have catalogued. Here is what its own listing supports, and what it will not tell you.
Everyone in this category says they tested twenty vacuums. We have not tested any, and we say so. What we do instead is read the manuals, compile the published specifications, and work out what each machine costs to run for three years — the method is written out in full.
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The verdict: buy it for what it is, which is a spot cleaner, and do not expect the listing to tell you much. The Little Green Max Pet 3860 publishes a two-tank system, 8.2 lb, a self-cleaning Tough Stain Tool and a pet hair tool. It does not publish a tank capacity in any unit, a hose length in feet, a cord length, a motor rating or a warranty term. That is an unusual number of blanks for a machine this popular, and it is the single most useful thing a review can tell you before you buy.
What a Little Green actually is
It is a portable extractor: a small two-tank machine that sprays a water-and-solution mix onto a fabric surface, agitates with a hand tool, and sucks the dirty liquid back out into a separate tank. That last step is what separates it from a spray bottle and a cloth, and it is the reason the category exists — the soil leaves the room in the dirty tank instead of drying back into the fibers.
What it is not is a carpet cleaner for a carpet. It has no powered floor head and no width; cleaning a room with one would take a weekend. It is built for a stain, a car seat, a sofa cushion, a stair tread or an accident on a rug. The full-size machines that do rooms are here, and buying a Little Green expecting one of those is the most common way people are disappointed by it.
What Bissell publishes for the Max Pet 3860
Bissell's own published specification for this model, as read from its retail listing.
Figure
Published value
Tank system
Two-tank, clean and dirty separated
Tank capacity
Not published in ounces or liters
Weight
8.2 lb
Suction claim
"30% more powerful" than an unnamed competitive portable deep cleaner
Self-cleaning
One-touch hose and tool cleanout on the Tough Stain Tool
Tools
Self-cleaning Tough Stain Tool, specialized pet hair removal tool
Formula
8 oz trial of PET PRO OXY with urine eliminator; ongoing purchase required
Hose and cord
Described as longer than the brand's smaller models; no length in feet
Heat
Not published
Motor rating
Not published
Warranty
Not published on the listing
Every row is Bissell's own published wording for this model. Where a row says "Not published", we could not find the figure on the listing and have not estimated one.
The three blanks that matter most
1. No tank capacity, in any unit
On a portable extractor, tank size decides how much you can clean before walking to a sink — and on the dirty side, how much you can lift before stopping. Bissell publishes the two-tank design and not the volume of either tank, which makes this machine impossible to compare numerically with its own siblings or with Hoover's. It is the single most conspicuous omission on the listing, and it is why this model does not score higher on our rubric than it does.
2. "30% more powerful" than what?
The suction claim names no comparator model and no measurement method. Thirty percent more powerful than which competitive portable deep cleaner, measured how? A percentage against an unnamed machine is a marketing sentence rather than a specification, and we treat it as one. It may well be true. It is simply not checkable, and no buyer can act on it.
3. No published warranty term
Bissell publishes warranty terms on plenty of its machines — the CrossWave Pet Pro elsewhere on this site publishes three years. This listing publishes none. On a machine with a pump, seals and a motor that meets water every time it runs, that blank is worth noticing before purchase rather than after.
How the Little Green line splits
Bissell sells several machines under the Little Green name and the differences are real:
Little Green Max Pet (3860) — the flagship of the line and the machine this review covers. Corded, 8.2 lb, self-cleaning tool, pet hair tool, and the longest hose and cord in the range according to Bissell, though without a figure.
Little Green Pet Pro (3909) — the long-standing mainstream model, and the one most people picture when they hear "Little Green".
Little Green Mini (4015) — cordless and much smaller, which trades runtime and tank size for the ability to work in a car without an extension lead.
The honest way to choose between them is the hose. If the machine will live in the house and clean sofas and stairs, the corded models have the reach and no runtime limit. If the real job is a car interior parked away from an outlet, the cordless Mini exists for exactly that and nothing else on this page can do it.
#
Product
Best for
Score
Price
01
Bissell Little Green Max Pet Portable Carpet Cleaner (3860)The self-cleaning stain tool is the feature that decides whether a portable gets used twice, and this is the cheapest machine here that publishes one alongside a pet hair tool.
Bissell Little Green Pet Pro Portable Carpet Cleaner (3909)The Little Green with a bigger tank and Bissell's strongest published suction claim in the portable line.
Bissell Little Green Mini Cordless Portable Carpet Cleaner (4015)The only spot cleaner on this site with no cord, which matters more than any suction claim when the mess is on a stair tread or a back seat.
The Little Green Max Pet alongside the three portable spot cleaners it is most often cross-shopped with. Scores are our rubric applied to published specifications, not test results.
01 · Most tools in the box
Bissell Little Green Max Pet Portable Carpet Cleaner (3860)
The self-cleaning stain tool is the feature that decides whether a portable gets used twice, and this is the cheapest machine here that publishes one alongside a pet hair tool.
Two-tank, clean and dirty separated. Capacity not published in ounces or liters
Suction claim
30% more powerful than "the competitive portable deep cleaner" — the machine it is compared against is not named
Self-cleaning
One-touch hose and tool cleanout on the Tough Stain Tool
Tools
Self-cleaning Tough Stain Tool and a specialized pet hair removal tool
Formula
8 oz trial of PET PRO OXY with urine eliminator; ongoing purchase required
Hose and cord
Published as longer than the brand's smaller models; no length stated in feet
Warranty
Not published on the listing
Every figure above is the manufacturer's own published number. Where a manufacturer publishes nothing, the row says "Not published" rather than an estimate.
What the numbers say
+A self-cleaning hose and tool rinse, published — the single feature that stops a portable turning into a smelly cupboard ornament
+A dedicated pet hair removal tool in the box, which the cheaper Little Green Mini does not include
+Two-tank separation is published, so dirty water never goes back down the hose
Where it stops
−Bissell publishes no tank capacity in any unit, so it cannot be compared with the Hoover's stated 1.18 liters
−The 30% suction claim names no competitor and no test method, which makes it unverifiable
−No warranty length published on the listing
Who it is for
Pet households that want the rinse-out tooling without stepping up to the larger Pet Pro, and are willing to accept an unpublished tank size.
Skip it if
You need to know how many trips to the sink a job will take. With no published tank figure, the one number that decides how a portable feels to use is missing.
Our score: 6.5 out of 10
Tank capacity5.0
Brush system4.0
Tools and reach9.0
Weight and handling8.0
Running cost6.5
Scored against the published rubric on How We Pick. These are judgments about spec sheets, not measurements.
02 · Biggest portable tank
Hoover CleanSlate Plus Portable Spot Cleaner
A 40-ounce clean tank in a 9.4 lb body — more than double the Little Green Mini's capacity for spot work.
Every figure above is the manufacturer's own published number. Where a manufacturer publishes nothing, the row says "Not published" rather than an estimate.
What the numbers say
+40 oz clean capacity — a 7" wide tool with the tank to actually feed it
+Two tool widths, so it covers a rug as well as a crevice
+Hose rinse, which is the same smell-prevention idea as Bissell's HydroRinse
Where it stops
−9.4 lb is heavier than the Bissell Little Green Mini for the same category of job
−No powered brush
−Bigger footprint than a Little Green in a cupboard
Who it is for
People who use a spot cleaner often enough to resent a 16-ounce tank.
Skip it if
You want the smallest possible thing that lives under a sink. The Little Green Mini is 2.4 lb lighter and physically smaller.
Our score: 6.7 out of 10
Tank capacity7.0
Brush system4.0
Tools and reach8.0
Weight and handling7.5
Running cost7.0
Scored against the published rubric on How We Pick. These are judgments about spec sheets, not measurements.
03 · Best portable for pet accidents
Bissell Little Green Pet Pro Portable Carpet Cleaner (3909)
The Little Green with a bigger tank and Bissell's strongest published suction claim in the portable line.
Extra-large clean and dirty tanks — 8 oz formula included
Suction claim
Manufacturer states the strongest suction in its class, versus the leading competition
Tools
Crevice tool, pet hair removal tool, self-cleaning hose tool
Formula
Designed around Triple Action Pet Pro Oxy Spot & Stain with urine eliminator and StainProtect
Power
Corded
Weight
Not published on the listing
Every figure above is the manufacturer's own published number. Where a manufacturer publishes nothing, the row says "Not published" rather than an estimate.
What the numbers say
+Bigger tanks than the Mini, so a full room of spots is one fill
+Pet-specific tools are in the box rather than sold on
+Self-cleaning hose tool carried over from the Mini
Where it stops
−Bissell does not publish a machine weight or an exact tank volume for this model
−The suction claim is Bissell's own against an unnamed competitor
−Pet formula is the priciest of the Bissell consumables
Who it is for
Homes with a puppy, an old dog, or a cat with opinions.
Skip it if
The messes are dry rather than wet. For tracked-in dirt a vacuum is the tool; extractors are for liquids and set stains.
Our score: 6.6 out of 10
Tank capacity5.5
Brush system4.0
Tools and reach8.5
Weight and handling8.5
Running cost6.5
Scored against the published rubric on How We Pick. These are judgments about spec sheets, not measurements.
04 · Only cordless portable here
Bissell Little Green Mini Cordless Portable Carpet Cleaner (4015)
The only spot cleaner on this site with no cord, which matters more than any suction claim when the mess is on a stair tread or a back seat.
Cordless. BatteryBoost+ rated up to 20 minutes of cleaning
Weight
7 lb
Dimensions
19.25 in wide x 11 in long x 13.4 in high
Tools
4-inch Tough Stain Tool with a removable lens, plus a HydroRinse self-cleaning hose tool
Formula
8 oz Little Green formula included; ongoing purchase required
Tank capacity
Not published
Suction figure
Not published in any unit
Warranty
Not published on the listing
Every figure above is the manufacturer's own published number. Where a manufacturer publishes nothing, the row says "Not published" rather than an estimate.
What the numbers say
+No cord at all, which is the whole argument on stairs, in a car and anywhere without a nearby outlet
+7 lb — the lightest extractor of any kind on this site
+HydroRinse self-cleaning hose tool is published, so the hose gets flushed rather than left wet and dirty
Where it stops
−20 minutes is the published ceiling, and a battery that fades ends this machine the way it ends any cordless
−Neither tank capacity nor any suction figure is published, so two of the three numbers that decide a portable are missing
−No warranty length published on the listing
Who it is for
Stairs, cars and upstairs bedrooms — anywhere the cord, not the suction, is the thing that stops you reaching for the machine.
Skip it if
The job is a whole room or a recurring deep clean. Twenty rated minutes and an unpublished tank make this a spot machine, and running out mid-stain is worse than dragging a cord.
Our score: 6.5 out of 10
Tank capacity4.0
Brush system4.0
Tools and reach8.5
Weight and handling9.5
Running cost6.5
Scored against the published rubric on How We Pick. These are judgments about spec sheets, not measurements.
The main rival, on published figures
Hoover's CleanSlate Plus is the machine most often cross-shopped against the Max Pet, and it makes the comparison awkward for Bissell in one specific way: Hoover publishes figures where Bissell publishes adjectives. Both are capable machines from brands with real parts networks. Only one of them lets you check what you are buying, and on a site built around published specifications that difference is the review.
That is not a reason to avoid the Little Green. It is a reason to buy it on its design — the self-cleaning tool is genuinely useful, and the two-tank system is well proven — rather than on its numbers, because the numbers largely are not there.
Who should buy it
Pet households with fabric furniture, where accidents and ground-in hair are recurring rather than occasional. The pet hair tool and the oxy formula are aimed exactly here.
Anyone who hates cleaning a dirty tool after cleaning a dirty sofa. The one-touch self-cleaning cycle on the Tough Stain Tool is the best-argued feature on the listing.
Households that already own a full-size vacuum and need the spot machine, not the other way round.
Who should not
Anyone hoping to clean carpets with it. No powered floor head, no width, no published tank. A full-size machine is the tool for rooms, and it is not much more expensive.
Anyone who needs to know the numbers first. If a missing tank capacity, hose length and warranty term bother you — and they reasonably might — Hoover publishes more.
Anyone cleaning a car parked away from the house. The corded models need an outlet; the cordless Mini is the model for that job.
We have not used this machine. Everything above is read off Bissell's own published listing and compared with other manufacturers' published listings. A spec sheet cannot tell you how the self-cleaning cycle performs after a year, how heavy 8.2 lb feels held at arm's length on a stair, or whether a stain lifts on the first pass. Our method page states exactly where our evidence stops and why we publish a score anyway.
Common questions
Is the Bissell Little Green worth it?+−
As a spot cleaner for pet accidents, upholstery and car seats, yes — the two-tank design is well proven and the self-cleaning Tough Stain Tool on the Max Pet is a genuinely good idea. As a carpet cleaner for rooms, no: there is no powered floor head and no width, and a full-size machine costs little more. Be aware that Bissell publishes no tank capacity, hose length or warranty term for this model.
What size is the Little Green tank?+−
Bissell does not publish a tank capacity for the Max Pet 3860 in ounces, liters or any other unit — only that the system uses two separated tanks. We have not estimated one. It is the most conspicuous blank on the listing, and it makes the machine impossible to compare numerically with rivals that do publish the figure.
Can the Little Green clean a whole carpet?+−
Not practically. It has no powered floor head and cleans a hand-tool's width at a time, so a room would take hours. It is designed for a stain, a cushion, a stair tread or a car seat. For rooms, a full-size upright extractor is the right machine and the price gap is smaller than most people expect.
What is the difference between the Little Green models?+−
The Max Pet 3860 is the flagship: a self-cleaning Tough Stain Tool, a pet hair tool and, per Bissell, the longest hose and cord in the range. The Pet Pro 3909 is the long-standing mainstream corded model. The Mini 4015 is cordless and much smaller, which trades tank size and runtime for the ability to clean a car parked away from an outlet.
Do you have to use Bissell formula in a Little Green?+−
The machine ships with an 8 oz trial and Bissell states that ongoing formula purchase is required. That is the real running cost of every portable extractor and it does not appear in the advertised price. Bissell states the requirement openly on this listing, which is more than some rivals manage.
Does the Bissell Little Green heat the water?+−
The Max Pet 3860 listing publishes no heating claim, so we do not credit it with one. Some portable extractors publish heated cleaning as a feature; where a machine does, we say so on its card. Where it does not, we write "Not published" rather than assume.
Sources
Manufacturer-published specifications — Every runtime, wattage, capacity, weight, filtration and warranty figure quoted on this page is the manufacturer's own published number for that model, retrieved September 1, 2026. Where a manufacturer publishes no figure, the page says 'Not published' rather than estimating one.
Sweep & Suction — How We Pick — Our published method, including the scoring rubric, the three-year running-cost formula and an explicit statement of what published specifications cannot tell you.
