You’re renting in Japan, the room you actually spend time in has no working air conditioner, and your landlord won’t let you drill a hole in the wall for a proper split system. So you start looking at those box-shaped “portable” or “spot” coolers (スポットクーラー) on Amazon and Yodobashi’s site, and you have no idea whether they cool a room or just make it damp and loud.
I looked into this because three separate people asked me a version of the same question while furnishing an unfurnished apartment here. Two were on 1-year contracts and didn’t want to pay for a split AC installation they’d have to rip out when they left. One lived in a share house where the landlord said no to any wall work, full stop.
All three landed on the same two brands: Corona’s どこでもクーラー line and Iris Ohyama’s portable coolers. They’re not the same kind of product, and mixing them up is the single most expensive mistake you can make here. Here’s what each one actually does, with real specs and real prices I checked this week.
How a portable AC is different from the split unit on your wall
A split air conditioner has two boxes. The indoor unit on your wall, and the outdoor compressor bolted to the balcony, connected by a pipe carrying refrigerant. That’s why it needs a technician, a drilled sleeve through the wall, and usually your landlord’s sign-off.
A portable unit crams the compressor and the cooling coil into one box on casters. It sits on your floor and vents hot exhaust out a flexible duct that runs through a panel clipped into your window frame. No drilling, no technician, no permission needed in most cases. I’d still tell the landlord, since a duct hanging out the window is visible from the street.
The catch is efficiency. The unit pulls in room air to cool its compressor, then blows that air outside. Your apartment has to replace that air from somewhere, so warm outside air gets sucked in through every gap in the building. This is the “makeup air” penalty, and it’s well documented for portable ACs everywhere. The machine spends part of its capacity fighting a leak it created.
Which means a portable unit is built for one job: cooling a single room, within a specific size range, in a place where a split system is either against the rules or a poor financial call for a short stay.
What Corona’s Doko Demo Cooler actually delivers, and what it doesn’t
Corona has been making heaters and dehumidifiers in Japan for decades, and its どこでもクーラー (“cooler anywhere”) line is the name most people in this category recognize. It runs a twin rotary compressor, the same core technology a wall-mounted air conditioner uses, and does three jobs: spot cooling, indoor laundry drying, and dehumidifying.
Here’s the part the product photos don’t make obvious, and it matters more than any spec on the box: Corona doesn’t sell this as a room air conditioner. Its own product page says so directly. Translated: “unlike an air conditioner, this cannot cool an entire room. If used in a closed-up space, room temperature may actually rise.” That second part isn’t a typo. Run it in a sealed room and it can make things warmer, because the exhaust heat has nowhere to go but back into the room with you.
The “11 tatami mats in wood construction, 23 tatami mats in reinforced concrete” number you’ll see on the box is labeled 除湿面積, dehumidification area, on Corona’s own spec sheet. It’s not a cooling-area rating. Corona sizes and rates this machine as a dehumidifier and clothes dryer that happens to blow cold air, not as a room cooler sized the way a real portable AC or a split system is sized.
What it’s actually good at: point it at your desk, your futon, or a rack of drying laundry, and it’ll cool that spot and pull real moisture out of the air around it. It’s rated for 9 to 10 litres of dehumidification a day, and the air coming out of the nozzle runs roughly 10 to 11°C below room temperature. That’s genuinely useful during rainy season, or for a hot desk. It will not bring your whole room down to 26°C the way a real portable AC or a split system will, and Corona doesn’t claim it does.
Affiliate disclosure: As an Amazon Affiliate link, I earn from qualifying purchases. Barely enough for a coffee.
Amazon Japan had it around ¥27,800 in mid-August 2026, with only one unit left at that seller, the usual sign of a model being cleared out. That’s because it’s previous-generation stock. Corona’s current 2026 lineup is the CDM-1026, CDM-F1026, and CDM-1426, all sharing the same twin-rotary design with modest updates to noise and tank life. I couldn’t find the 2026 models listed on Amazon Japan at all during this check, only through Yahoo Shopping, Rakuten, and kakaku.com-linked retailers, at prices from roughly ¥33,000 up. So the honest tradeoff: if you want the current model, you’re not buying it through Amazon right now, and you’ll pay more for it. If you’re fine with previous-generation stock and want the Amazon-affiliated purchase, the CDM-1023(AS) is cheaper, in stock while it lasts, and functionally the same machine.
What you get from Iris Ohyama’s two sizes
Iris Ohyama started in plastics and home goods and has spent the last decade muscling into appliances, usually undercutting the traditional makers on price while matching them on basic function. Unlike the Corona unit above, these are genuine portable air conditioners: they vent hot exhaust outside through a window duct and they’re rated and designed to cool a room, not just dehumidify one. Their portable line splits into two size tiers.
The smaller one, the IPP-2224S that used to sit here, has been discontinued at Iris’s own store. Its 2026 successor is the IPP-2226S-W, rated for 4.5 to 7 tatami mats, so a single bedroom. Cooling output is 2.0/2.2 kW depending on frequency, power draw is 650/730W, and it runs off a normal 100V outlet with no special wiring. It uses R32 refrigerant. Amazon had it at around ¥30,777 in mid-August 2026, up from the roughly ¥20,000 the outgoing model sold for, but it’s still the cheapest real compressor-based cooling you can put in a Japanese room without an installer.
If noise is your bigger worry than price, Iris also sells an inverter version of the same size class, the IPP-2226SV-W, which ramps the compressor up and down instead of cycling on and off at full power. I couldn’t pin down a firm August 2026 price for it in this check, so compare it against the IPP-2226S-W yourself before deciding it’s worth the premium.
The bigger one, the IPP-2825U that used to be recommended here, has also been superseded, by the IPA-2826U-W, 2.8 kW output, rated for 7 to 10 tatami mats. It’s actually priced better than the outgoing model, on sale for around ¥44,600 in mid-August 2026 (down from a reference price of ¥48,480), against roughly ¥50,600 to ¥54,000 for the older IPP-2825U. This is the one for a studio or a combined living-dining space.
Prices on all of these bounce around between Iris Ohyama’s own store, Amazon, and Rakuten, sometimes by ¥15,000 for the same model in the same month. Check all three. Assuming Amazon is cheapest has cost people real money in this category.
How the price compares to a real split system
The sticker prices at a 家電店 make split systems look like the expensive choice. At the cheap end of the portable range that holds up. At the expensive end the two categories almost touch, and most people never check.
On 3 August 2026, the Daikin S226ATES-W (the 2026 E series unit sized for a 6-jō room) was ¥69,800 on Amazon Japan, and the Mitsubishi Electric MSZ-GV2226-W in the same size class was ¥68,000. Those are unit-only prices. Standard installation is quoted separately and typically adds tens of thousands of yen depending on pipe run, floor, and whether the sleeve through the wall already exists, so get an actual quote rather than trusting a range you read online.
Put the two side by side for a 6-jō bedroom. The IPP-2226S-W at around ¥30,800 buys you cooling this weekend, with zero installation and zero landlord conversation. A Daikin split at ¥69,800 plus install costs several times that, but it’s quieter, more efficient per hour of running, and it stays on the wall instead of eating a square metre of your floor.
Now do the same comparison at the top of the portable range. The IPA-2826U-W at around ¥44,600 is within shouting distance of a 6-jō split unit before installation. If your landlord allows a split and you’re staying more than a year or two, spending that much on the less efficient machine is hard to justify. The portable makes sense at the bottom of the range and at the top only when a split is genuinely off the table.
If you want the longer version of how Japanese split systems are built and why they look nothing like the window units you grew up with, I wrote that up separately: Why Japanese air conditioners look different from the rest of the world.
Do the tatami mat ratings actually mean anything
For the two Iris Ohyama units above, yes. Treat the tatami mat (畳, jō) number on the box as a hard ceiling. These figures come from JIS testing standards, the same ones that apply to full split systems, so they’re measured rather than invented by a marketing department. But they assume a reasonably insulated Japanese room at a specific temperature difference.
For the Corona unit, the tatami number is a different thing entirely, a dehumidification-area figure, not a cooling-area one, as covered above. Don’t compare it directly to the Iris numbers.
Live in an older wood-frame apartment with single-pane windows, which is extremely common outside newer builds, and an Iris unit rated for 7 tatami mats will struggle to hit that on a real Tokyo August afternoon. Your walls and glass leak heat back in about as fast as the machine pulls it out.
My rule of thumb, and this is engineering judgment rather than a number off a spec sheet, so treat it as such: buy one size category up from what the room measures if your building is older, or if you’re on the top floor with direct sun.
The other thing to check before you order: window compatibility. The exhaust panel these ship with is designed for a standard sliding window. If your place has casement windows that crank outward, or a balcony door where the window should be, you’ll need foam board and some improvisation, or an adapter kit. Confirm this before the box arrives, not after.
Noise, and what running one actually costs a month
Noise matters more here than with a split system, because the compressor is in the room with you instead of bolted to an outside wall.
Corona rates the CDM-1023(AS) at 49dB in normal operation, dropping to the mid-30s in its quiet setting. Roughly the difference between a conversation and a library. Iris Ohyama doesn’t publish a dB figure for the IPP-2226S-W on its spec sheet, but the outgoing IPP-2224S was rated around 55.7dB, closer to a dishwasher running in the next room, and there’s no indication the new model is meaningfully quieter unless you pay up for the inverter IPP-2226SV-W. If you work from home or you sleep light, that gap deserves more weight than the price difference between models.
On running cost, take the IPP-2226S-W at 730W on its 60Hz setting. Six hours a day at Japan’s residential electricity rate, averaging somewhere around ¥31/kWh as of early 2026 (this moves with fuel costs and your regional utility, so treat it as a planning number and check your own tariff), comes to roughly ¥136 a day, or about ¥4,080 across 30 days of daily use. That’s one scenario. Run it longer on a hot August day and the bill climbs with it.
That figure runs meaningfully higher than a modern inverter split system doing the same job, for the makeup-air reason above. The compressor works harder for the same result.
Maintenance you can’t skip
Both of these double as dehumidifiers, which means you’ll run them hard through rainy season (梅雨) and for drying laundry indoors. That water has to go somewhere. The CDM-1023 holds about 5.8L in an internal tank you empty by hand, though some units in this class support a continuous drain hose if you’re near a floor drain.
Check the tank capacity before buying if you plan to run it overnight. A full tank triggers an auto-shutoff, and waking up at 3am to a warm room and a beeping machine is one of the most common complaints in user reviews for the whole category.
Filters need a wipe every couple of weeks under heavy use, same as any AC. Neither brand markets a 10-year filter the way Daikin and Sharp do on their split systems, so budget a few minutes a month.
Where to buy one
Yodobashi Camera and BIC Camera both stock these in person, which is worth a trip before committing floor space. These are bigger than product photos suggest, closer to a large suitcase standing on end than a tower fan.
Online, Amazon Japan, Rakuten, and each maker’s direct store (Iris Plaza for Iris Ohyama, normal retail channels for Corona) carry the same models, though as noted above, Corona’s current-generation stock is easier to find outside Amazon right now. I’ve watched the same unit sit ¥10,000 apart between them in the same week depending on whether a sale was running. If you’re not desperate, compare all three, especially heading into peak summer when everything climbs.
One warning if you’re eyeing a used one from a リサイクルショップ. These have a compressor with moving parts and a refrigerant charge, the same failure points as a real air conditioner. A secondhand one with unknown history is a much bigger gamble than a secondhand microwave. If you go used, ask when it last ran and whether it still holds a charge, rather than just checking that the fan spins.
Quick answers to what people actually ask
Do these work in Japan’s humid summer, or do they just move humid air around? The Iris Ohyama units cool and dehumidify at the same time, using a real compressor-based refrigeration cycle. The evaporative “swamp coolers” sold for dry US climates work on a completely different principle and would be miserable in Japan, and neither Corona nor Iris Ohyama sells that type here. So yes, the Iris units handle humidity within the room size they’re rated for. The Corona unit dehumidifies well but isn’t trying to cool your whole room in the first place.
Can I use a portable AC without venting the exhaust hose outside? Skip the exhaust setup on an Iris Ohyama unit and you’ve bought a space heater. The heat pulled out of your room air has to go somewhere, and without the duct it goes straight back into the room, plus the compressor’s own waste heat on top. Every listing ships a window panel for exactly this reason. Install it. The Corona unit doesn’t have this option in the first place, since it has no outside vent at all, which is exactly why it can’t cool a whole room.
Will it lower my humidity enough to skip a separate dehumidifier? For a single room, usually yes, and this is where the Corona unit genuinely shines, since it’s built around clothes drying as much as cooling. If rainy-season laundry smell is your only problem and you don’t need summer cooling, the Corona unit or a dedicated dehumidifier is the right call. If you actually need the room to get colder, that’s an Iris Ohyama job.
Do I need to tell my landlord? Legally, in most rentals, no, since nothing is being fixed to the building. Practically, yes. A duct hanging out the window is visible from outside and neighbours ask questions.
So when do you actually need one instead of a split AC
Get an Iris Ohyama portable if you’re on a lease that forbids wall installation, if you’re in a share house, or if you need supplemental cooling in one room your existing split system can’t reach, like a home office in a converted room or a loft that bakes.
Get the Corona unit if what you actually have is a laundry-drying and humidity problem, with occasional spot cooling as a bonus, not a room that needs to get cold.
Get the split system if you’re signing a longer lease and your landlord allows it. It’s more efficient, quieter at the same cooling output, and it doesn’t eat a square metre of floor.
And if you’re furnishing a whole apartment from scratch and trying to work out where the AC budget sits against everything else you need to buy, I wrote up the full breakdown a while back: Guide to getting air-conditioner for new life in Japan.
Prices checked on Amazon Japan and kakaku.com, mid-August 2026. Specs from Corona and Iris Ohyama’s own current product and spec pages. Electricity cost is a planning estimate, not a quote.
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