Japan Today



Reviewing the economics of air conditioner use


So far this summer, Japan has been pretty damn hot. To advise its readers on the practical aspects of using their air conditioners at home, Nikkan Gendai (July 5) devotes nearly an entire page to an informative multiple choice questionnaire, which was produced based on findings from a nationwide survey of 4,000 air conditioner users by the research laboratory of electronics maker Panasonic.

For example, air conditioner performance was tested by turning off and "resting" AC units for 5 minutes after each 30 minutes of operation to check for power savings. The result clearly showed that leaving the unit on resulted in lower power consumption.

Q 1. How much less power is consumed by "leaving it on"?

A. 10%

B. 20%

C. 30%

Correct answer: C (30%)

In the case of certain Panasonic products, power savings can be realized with its "Eolia application," which notifies you if you've neglected to turn off the unit. The app also calculates and displays power charges.

Q 2: If power consumption when using the air conditioner set temperature of 26 degrees Celsius is rated at 100, what will the change be when the temperature setting is raised by 2 degrees (to 28 Celsius) and a circulator fan is also used?

A. 102

B. 98

C. 78

Correct answer: C (78)

According to tests conducted by TEPCO Laboratories in Yokohama, proper use of a fan to circulate chilled air can result of savings in power consumption of up to 22%. Changing the temperature setting to 27 degrees will still save power by 9% compared with not using a fan.

Q 3: It seems that many people set their AC units to the "dehumidification/dry" mode on humid, muggy nights. But will the "dehumidification" setting achieve more, or less, dehumidification than the "cool" setting?

A. more

B. less

C. no change

Correct answer: B (less)

Lab tests found that "cool" removed 2.3 kilograms of water per hour. Under identical conditions, dehumidification only removed 1.1 kilograms.

Q 4: One often-overlooked aspect of air conditioner energy conservation is the placement of so-called outdoor units. Recently, calls for putting outdoor units in the shade have become widespread. But how much energy can be saved by moving outdoor units from an ambient temperature of 35° C to 30° C?

A. 22%

B. 33%

C. 42%

Correct answer: C (42%)

Also gained by extending the space from the unit's exhaust and building wall to enable better circulation.

Q 5: In TEPCO's service area, appeals for power conservation are often issued between 3 p.m. and 6 p.m., the period of highest demand. But what time of day is the peak demand for so-called "residential electricity"?

A. Noon to 2 p.m.

B. 3 p.m. to 5 p.m.

C. 7 p.m. to 8 p.m.

Correct answer: C (7 p.m. to 8 p.m.)

Q 6: What percentage of total power consumption does the so-called "residential use" represent?

A. 10%

B. 30%

C. 50%

Correct answer: B (30%)

Q 7: And finally this question: Air conditioning tends to be demonized as a power hog, but what percentage does it actually account for in terms of the total annual household power usage?

A. 2%

B. 20%

C. 30%

Correct answer: A. 2%

The low percentage can be attributed to the fact that the AC is only heavily used in homes for around three to four months of the year, and even then usually not operated around the clock.

Nikkan Gendai also offered some practical hints for realizing additional power savings at home. The percentage indicates potential savings if certain procedures are followed.

  1. Air conditioner: 5.4%

(Hint: 1.9% power savings from keeping the filter clean)

  1. Lighting 2.5%

(Hint: Lower brightness during daytime and turn off when not needed)

  1. Refrigerator 1.2%

(Hint: reduce the cooling setting from high to medium. Efforts should be made to reduce time the door is open, and interior should not be overstocked.)

  1. Television 2.0%

(Hint: reduce screen brightness and turn off when not viewing)

  1. Bidet-type toilet 0.3%

(Hint: Disconnect the power cord when not in use)

  1. Leaving appliances in quiescent (standby) mode: 0.5%

(Hint: if not using for a long time, disconnect from the wall outlet or power supply)

  1. Washing machine 0.4%

(Hint: Save power by running loads of less than 80% capacity)

  1. Clothes dryer (0.4%)

(Hint: Save power by running for shorter time and then hanging indoors)

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Original source, if you want the full picture some important details are missing like how dehumidifying uses way less energy despite removing less water.

5 ( +6 / -1 )

Recently, calls for putting outdoor units in the shade have become widespread.

When I stayed in Koh Samui in Thailand years ago, I noticed our stylish bungalow had Japanese air conditioners. But unlike in my home back in Tokyo, there were no unsightly units and ducts to be seen. I discovered the units were installed in an attic space under the roof, with the ducts running through the walls, away from the hot sun. My units at home in Tokyo are on the balconies, taking up precious space, with the ducts bolted to exterior walls, industrial style.

It would be nice if the Japanese made an effort to not just save energy (42% reduction, in this case) but also create more visually pleasing living spaces.

11 ( +12 / -1 )

When I stayed in Koh Samui in Thailand years ago, I noticed our stylish bungalow had Japanese air conditioners.

The only "Japanese" air conditioners actually made in Japan are Daikin. All other brands are built overseas.

-4 ( +3 / -7 )

The only "Japanese" air conditioners actually made in Japan are Daikin. All other brands are built overseas.


Our 2 brand new self installed 200v Hitachi’s were made in Japan. I also got some 1.8 meter stakes and zip tied a shade sheet over and on one side of them to block the sun. Wife’s idea and now I understand why. 43%? Wow.

4 ( +6 / -2 )

The only "Japanese" air conditioners actually made in Japan...

It was a Japanese brand and model whose design was identical to the ones found in most Japanese homes.

-1 ( +2 / -3 )



Our 2 brand new self installed 200v Hitachi’s were made in Japan.

Well, when I bought mine three years ago, it was only Daikin making their products in Japan. I'm glad to see that Hitachi has move its top end production models back to Japan.

-3 ( +0 / -3 )

Imagine how much more efficient your A/C would be if Japanese houses/apartments had any kind of decent insulation. 5cm of Styrofoam will not cut it. I know they power companies are all mighty, but you'd think that Japan trying to meet its commitments for cutting CO2 levels would think about this one simple but effective method!

5 ( +7 / -2 )

Nice article although simple calculation showes that aircons take 10% not 2% of the annual increase in the electricity expense! And I use them very sparingly with most of the points mentioned here cleared!

My neighbor uses his unit non stop and I'm sure it might be up to 20% increase in his bills!

I own Panasonic ACs - the 2 smaller models are foreign made while the bigger higher end model is made in Japan. Most of the makers do this for their different lines of products.

0 ( +2 / -2 )

Great article.

My favourite bit is where it says AC is only 2% of residential household electricity consumption. It's hardly anything and certainly not worth being kechi kechi (stingy) about. Way more energy is used in heating. What this means is that you should insulate/seal up your home like crazy to minimize heating, but not worry if your house still needs AC in summer. Traditionalists in Japan always go on about how old houses "breathe" and are build for cross ventilation, but heating them costs a fortune and produces tons and tons of CO2. A new house that is well sealed up and insulated will need next to no heating, but may still end up needing AC to stay cool. The energy required for this is very little compared to heating. Regarding the 2% figure, you have to remember than many people now cook and heat water with electricity.

I know the government is telling people to cut down on AC use, but that is because it has effed up the energy supply. It is not because AC is an energy hog. The same government is telling us to buy electric cars that will place a much bigger burden on the grid if plugged in at the same time.

I don't know where the compressors in Japanese air cons are made but there are only three sizes of them, typically sold as 6 mat, 10 mat, and 14 mat. All other sizes of air con use the same compressor. A 20 odd mat air con will cost much more than but have the same compressor as a 14 mat air con. The max power will be the same, with any difference due to throttling, not compressor capacity.

-2 ( +1 / -3 )

Interesting article for the season, a lot of people have erroneous concepts about the use of AC, some because of myths without any real basis, other because they no longer apply to newer machines that are much more economical; so it is good to see an effort to make the people better informed so they can make good decisions.

Sometimes I hear people telling how members of their families end up having to spend a night in the hospital because of heat shock because they did not want to "overuse" their ACs, this kind of articles can reduce that risk by providing some way to be economical with the electricity but still use it as needed.

-2 ( +1 / -3 )

Mr Kipling, actually I think our model was the last to be made in Japan. All newer models are made in the large “democracy” next door.

-2 ( +0 / -2 )

Freeze a big bottle of water,then put it your bed,and the melting ice will cold your body down all night,as the ice melt inside the bottle

-3 ( +0 / -3 )

re question 1, variable refrigerant flow(VRF) type ACs/heat pumps are designed to operate continuously where disrupting operation by manually switching them on/off will increase power consumption as well as wear & tear.

-1 ( +0 / -1 )

What a crazy shadow boxing or air guitar playing, when just only considered question and answer number seven. Are we really having to discuss everyday in detail and do all those media and private efforts because of those 2% of 30% residential use, resulting in a maximum of only 0.6% saving potential?

-1 ( +0 / -1 )

Most of our electricity Is supplied by roof top solar panels, so does this discussion apply to me?

-1 ( +1 / -2 )

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