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The story
A survey of 12 cities worldwide conducted by air conditioner manufacturer Daikin Industries found that Tokyo’s average daily air conditioner usage time was 14 hours and 12 minutes — the longest of any city surveyed. With the finding that 30% of households run their AC “almost all day,” the thread lit up with personal anecdotes that leaving the AC on all the time is actually cheaper, debates over home insulation performance, and comparisons with France’s notably low AC adoption rate.
8/26 (Wed) 13:21 JST
Yomiuri Shimbun Online
According to a survey on air conditioner usage across 12 cities worldwide conducted by major air conditioning manufacturer Daikin Industries, the average daily at-home usage time during the hottest period was longest in Tokyo, at 14 hours and 12 minutes.
Source: news.yahoo.co.jp / Read the original article here
What people said
It's not like you're running factories — show some restraint.
Lots of buildings and "tamamans" around. Buildings and tamamans throw off huge amounts of heat from their outdoor AC units.
That's not "tamaman," it's "tawaman" (tower mansion / high-rise condo), lol
Okutama folks, sit down and shut up. (Okutama is Tokyo's rural, mountainous — and much cooler — western edge)
Well, it's true that when people from western Japan come to Tokyo, they think 'huh, maybe I could actually get by without AC here?'
The humidity and sunlight are just that different.
That's just this year though…
Not turning it on at all for 24 hours is the most cost-effective, lol!
It's just that if you're only turning it off for 30 minutes, you're better off leaving it running.
An abnormally low number
Guess that's what you'd expect from an environmental leader, huh
If eco-terrorists spot your outdoor unit, they'll smash it
If you set it to 28°C, once it hits 28°C it basically goes silent
and barely uses any power — isn't that how it works?
Once the room hits 28°C, it'll just idle there for 10 or even 15 hours.
Back in the Showa era (roughly 1926–1989), it'd just blast cold air forever trying to reach 28°C,
overcooling the room and wasting tons of electricity.
If a Showa-era AC saw today's auto mode doing nothing, it'd say "If you're not gonna do anything, get out!"
I guess that's because inverter ACs are just standard now?
Though the era when that was a selling point was ages ago
Exactly, that's why I just leave mine running all the time now
I've got two units — one stops exactly at the set temp and runs quietly, but the other one cools down to 25°C even when I set the max of 30°C, and it's driving me nuts
because they're not very airtight
That was true for a lot of houses up through the Showa era, but new builds have high insulation now, so they actually cool efficiently
It's not about airtightness
Insulation performance is what matters
Airtightness is basically garbage-tier by comparison
Because it's not that hot there
Yeah right, that's a lie—
June…? That's freak weather… it's not normally that hot
Go check today's temperature
I heard new detached houses in Tokyo are now required to install solar power systems
Hearing that, I actually got solar installed myself this past February, lol
Sure, electricity's expensive, but if you look at your August bill, about 10% is knocked off thanks to government subsidies
this just turns into a classic 5ch thread where everyone argues past each other
based on their own personal standards
But that's the whole charm of 5ch, isn't it
Same story on any social media, honestly
and now we're in a full-blown feedback loop
It's over for planet Earth
I kind of want them to build even more data centers in the Kanto region and make it even more hellish (lol)
Just splash water on your outdoor unit
#keep it rain-level so it doesn't break
Honestly, I think this is exactly it
Also, the asphalt
Apparently there are cases where leaving it running costs less than switching it on and off constantly. The AC uses the most power right when you first turn it on in the heat
Background and Key Points
Daikin’s survey covers only the hottest stretch of summer, but the number matters because Japan runs on Tokyo Electric Power’s summer peak-demand warnings and a decade-old “Setsuden” (electricity-saving) culture born from the 2011 Fukushima disaster, when households were urged to set thermostats at 28°C rather than switch AC off entirely. That 28°C figure, which several posters treat as an engineering threshold, is actually a government-recommended “Cool Biz” target, not a technical optimum. Japan’s summer humidity, distinct from the dry heat of much of Europe, is also why direct comparisons to France’s roughly 20% AC penetration rate are misleading on both sides of the thread: it’s not simply an “eco-conscious France vs. wasteful Japan” story, since France’s oceanic/continental climate and historically low summer humidity made AC far less necessary there until recent heatwave summers changed that calculus.
The thread’s real fault line isn’t environmental guilt versus comfort — it’s a genuinely unresolved consumer question: whether leaving an inverter AC running continuously at a set temperature costs less than cycling it on and off, because compressors draw the most power at startup. Posters split between those citing inverter technology’s ability to idle near-silently once target temperature is reached, and those insisting any runtime beyond active cooling is waste.
What the thread never quite spells out is the insulation angle raised only briefly at the end: Japan’s building stock is unusually heterogeneous, with older homes (pre-1980s “Showa” construction) built with minimal insulation, while airtightness and thermal insulation are two distinct, often-conflated metrics only now being standardized under Japan’s newer energy-efficiency building codes — a policy shift far larger than anything the survey itself addresses.
*This article is excerpted and summarized from the 5ch (News Speed+) thread “[Survey] Tokyo’s AC Usage Longest Among 12 World Cities at 14 Hours 12 Minutes… 30% Run It Almost All Day”.
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