Has AC energy efficiency increased drastically in the last decade?

S

sauravghosh

Adept
Well I know nothing about ACs. I use a Hitachi window ac for my room, bought it back in 2011, 5-star and all those, back then it was supposed to be really power efficient. This is the particular model- https://photos.app.goo.gl/K4L4emGTFp33wjbM8

Anyway, I always run it on automatic mode and found that no matter what it consumes 1190 watts per hour. I use mine at night for six hours (1 to 7 am), so it consumes 1190x6 watts, so around 7 kwh for those six hours.

Now I would not have cared much, but just yesterday I found a Carrier inverter was selling on FK and I found that the energy rating chart on it shows that it consumes 650 units per year, for 1600 operating hours per year. That means like 4+ hours operation every day. It looks like the consumption is one third of mine. This is the model I glanced at-
https://i.imgur.com/hlYCL35.jpg

Then yesterday I found this video on youtube-

Guy shows that ac consuming 2.3 kwh after a 8-hour run at night! That's like less than 300 watts per hour on average, while mine is 1190 watts per hour. I mean WTF.

My main question is, are all these true? Is my unit really that power hungry compared to latest models?
 
Yes your window AC is really inefficient. Even a modern inverter window AC is not as efficient as a inverter split ac.

My 1.5 ton Daikin 5 star ISEER 5.2 AC, once it reaches the desire temperature set between 24 to 26c, it consumes as low as 240 to 280 watts late at night or early morning.

Some 5 star Inverter AC use bldc motors for the blower, ODU fan and the compressor. So you really start saving power.

Since the inverter compressor is for the most part continously running, the compressor needs to spin at 50% speed to theortically match the fixed speed compressor that turns On (runs at fixed max speed) and Off based on my own crude comparison. Even if the inverter compressor runs say at 60% to 70% speed it will still save because of the bldc motors which simply consume less and there is also no inrush current every 5min or so like in the fixed speed compressor each time it starts.
 
I have a 5 yrs old Samsung 5 star AC.
I keep the setting as:
Initially 18C for half hour to cool the room and then to Auto mode 24C or 26C
With 6 hours of timer to shut it off auto.
My rooms ceiling Fan is also spinning on 1 the lowest speed.

The AC blows cold air for say 10 mins where the compressor can be heard kicking in and working. It then eventually stops/the compressor goes into standby and simply keeps blowing cool fan air thereafter for another 10-15mins until the cooling starts again.
Does this behavior actually helps save power or does it consumes more power?

Just wanted to know roughly my Unit power consumption for these 6-7 hours on a per night basis.
No I don't intend to invest or install any measuring device but just a rough estimation.
 
The star stop times of the compressor varies based on set temperature amd ambient temperature (both outdoor and indoor air). But when it does start it's going to consume more power like 10x for 2 seconds or more vs a bldc motor of the inverter AC which has no inrush current and even when it's running at full speed, it still consumes much less.

Ceiling fan makes sense if you have a floor above your ceiling but if the room being cooled is the top floor, then it's better to use a pedestal fan which is also of bldc. Wish xiaomi launched their pedestal bldc fan. The current bldc pedestal fans in India like from luminous and gorilla consume 20w at speed one, which is a lot compared to a bldc ceiling fan which consume around 6w at speed 1.
 
Thanks all for your inputs. Well, seems like I will be getting a new AC. I can't stand high power usage. If anyone has any recommendation, kindly shoot. Don't have budget of purchasing a 50k or even 40k AC really. So probably Daikin and Hitachi out of the window. Is Carrier a good brand?

One thing I need to understand first is how much tonnage I need. I checked my room's measurements, jeez what a hard task, and it is something like 14x10x10 (LxWxH) and there's about 30 sq.ft of wooden windows (one east facing, other south facing). Inputting the same on Bluestar's and General's site show me I only need 1 ton! Yet the same measurements on Carrier's side shows me I need a 2 ton. What the heck!

My current one, the windows Hitachi, which is supposedly a 1.1 ton unit, takes about 90-100 mins for the first compressor cut out, which happens when the room temp reaches around 25 degrees I have noticed, from 33 degrees. So is 1.2 ton enough or should I look for 1.5 ton?
 
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Go for a 1.5 ton Inverter AC. Getting a 1.2 inverter will be difficult.
3 star 1.5 ton inverter models from LG/Panasonic or 4 star inverter from Voltas should fit in your budget of less than 40k.
 
jujuburi said:
Anyway, I always run it on automatic mode and found that no matter what it consumes 1190 watts per hour. I use mine at night for six hours (1 to 7 am), so it consumes 1190x6 watts, so around 7 kwh for those six hours.
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Have you measured this with some watt meter ?

Forget what the label says. Their testing conditions and your use case can be very different. As can be the case with the guy in the video. You both could have the same AC but the power consumption values may differ for the same settings. How big the room is, did he mention how big his room is in the video ? How big is yours ? how many times doors are opened. heat sources in the room etc. Which direction room faces, top floor, below, how much sun does it get etc. How humid. How many people in the room. AC's also remove moisture, more moisture longer they work. Many variables can influence power consumption with an AC.

Another thing i'm not clear on is do these inverter ac's tell the temperature. How reliable is such a reading when the thermometer is attached to the AC. Shouldn't it be a little distance away. Otherwise it will be consistently reading higher than it really is. Humidity will effect what it feels like as well. i've been in rooms that had the exact same temperature and felt very different from uncomfortable to bearable because there is some air circulation one and not the other. All this is building to the biggest variable of the lot. Personal preference. Would you be comfortable with the settings of others or do you prefer your own. Likely you have your own as its a function of all the other variables i mentioned. Saving 1-2 units per night which might work out to no more than Rs.300/month possibly less isn't going to matter if the net result is you sleep better in a cooler room by spending extra..

A fridge is simpler in this regard and even here i'm finding my power consumption values higher than what the four star sticker claims based on yearly consumption.

My main question is, are all these true? Is my unit really that power hungry compared to latest models?
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How much did you pay for your window unit. Compared to how much more you would have had to pay for an inverter unit back in 2011 ?

How much less was your window unit ?

My argument on this board few years before you bought your unit was the pay back time was like ten years away so it would be cheaper to buy a window unit like yours and stick with it until it died. Two star window unit costs less than 5 star. Doing the needful maintenance as and when necessary. The conclusion was stunning as some one with less money, less knowledge could end up spending less over the life of the unit ie TCO than some one who ponied up more for an inverter hoping to save on power. As the payback time was so far into the future as to be irrelevant. You were not saving money on power consumption, what you were buying was a quieter unit, compressor is outdoors after all. Only need to punch two small holes in the wall instead of getting a welder to remove grills to window install the unit. Better features. Maybe a more reliable, compact, nicer looking unit. This is where you money was going.

That situation might not hold true any more unless window units still remain as cheap as they were back then compared to inverter units. My assumption with that study was the cost differential remained constant over the years. Is that still the case ? if inverter tech is more common these days then inverter units would be cheaper. Payback time possibly sooner. Question is how much sooner.
 
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Leaving aside all the technical discussion and measuring which is the right way to go, the situation right now is so bad in the really hot places that it will be difficult to rely on just on star rating and efficiency. Other factors have to be considered.
To give you an e.g, I stay on top floor and the room temperature is 43 here in Noida. My new 1.5 ton Hitachi window AC ( 3 star ) is struggling. not only during day but night.
My friend who in similar situation, I told him to buy a Ogeneral window no matter what. And turns out it was the right decision as it does a much better job. Sure the investment was higher but its worth the ROI. We couldnt buy split as its rented accomodation so with everything in mind, its best to invest in best possible efficient , tonnage, brand and technology upfront. The situation is going worse heat wise and I see no other way thesedays.
 
puns said:
To give you an e.g, I stay on top floor and the room temperature is 43 here in Noida. My new 1.5 ton Hitachi window AC ( 3 star ) is struggling. not only during day but night.
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I guess people on top floors (in rented apartments) should always oversize when buying ac's. If the room calculations show 1Ton is enough, buy 1.5Ton or 2Ton. The top floors usually get heat from 2-3 sides during the day and the cement walls don't cool down that fast during the night. This makes such apartments like ovens 24/7.

If not living in rented apartment ask building society to put up cement sheets on terrace. Many buildings have started putting up those cement sheets on the terrace to reduce heating on top floors and stop rain water seepage into building walls. Those cement sheets help a lot in bringing down the temps by 2-3 degrees. The property tax will go a bit higher since its counted as an additional floor by municipality.
 
6pack said:
I guess people on top floors (in rented apartments) should always oversize when buying ac's. If the room calculations show 1Ton is enough, buy 1.5Ton or 2Ton. The top floors usually get heat from 2-3 sides during the day and the cement walls don't cool down that fast during the night. This makes such apartments like ovens 24/7.

If not living in rented apartment ask building society to put up cement sheets on terrace. Many buildings have started putting up those cement sheets on the terrace to reduce heating on top floors and stop rain water seepage into building walls. Those cement sheets help a lot in bringing down the temps by 2-3 degrees. The property tax will go a bit higher since its counted as an additional floor by municipality.
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Thanks for tip. My landlord is cool so I will ask him for this cement sheet for terrace. Is it like 1 sheet or multiple sheets on top of each other ?
 
6pack said:
The property tax will go a bit higher since its counted as an additional floor by municipality.
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How does adding a sheet to the terrace get counted as an additional floor ?

In Bangalore they set the tax based on the kind of roof. RCC is the top level which most appts would be anyway.
 
puns said:
Thanks for tip. My landlord is cool so I will ask him for this cement sheet for terrace. Is it like 1 sheet or multiple sheets on top of each other ?
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It's like small sheets overlapping one another mounted on top of slanting steel and GI pipe frames.
The edges have a small plastic gutter to catch rain water and direct it away from the building. Some buildings use that rainwater for rain water harvesting.

blr_p said:
How does adding a sheet to the terrace get counted as an additional floor ?

In Bangalore they set the tax based on the kind of roof. RCC is the top level which most appts would be anyway.
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It's additional FSI. Adding cement cover which is permanent will count as additional floor. So additional tax each house will end up paying.
 
6pack said:
It's like small sheets overlapping one another mounted on top of slanting steel and GI pipe frames.
The edges have a small plastic gutter to catch rain water and direct it away from the building. Some buildings use that rainwater for rain water harvesting.
Click to expand...
This means you lose the entire space where these sheets are installed. Maybe for areas where there is no foot access.

It's additional FSI. Adding cement cover which is permanent will count as additional floor. So additional tax each house will end up paying.
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Can you post a pic i don't think i've ever seen such things before.
 
i too have a hitachi 2011 model like yours. Lately cooling is reduced a lot, do i need a gas topup ? what else could be wrong to lower cooling power. ac was pressure cleaned at season start.
 
RakaKaKaka said:
i too have a hitachi 2011 model like yours. Lately cooling is reduced a lot, do i need a gas topup ? what else could be wrong to lower cooling power. ac was pressure cleaned at season start.
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I too had this same problem with an older split a/c with the cooling not being maintained even after servicing. Later found out that it is due to the voltage fluctuation problem. The compressor does not start when there is low voltage or if the voltage fluctuates. The standard stabilizer does not boost the voltage. I had to buy a double booster stabilizer to overcome this voltage problem. Now it is working properly.
 
6pack said:
It's like small sheets overlapping one another mounted on top of slanting steel and GI pipe frames.
The edges have a small plastic gutter to catch rain water and direct it away from the building. Some buildings use that rainwater for rain water harvesting.



It's additional FSI. Adding cement cover which is permanent will count as additional floor. So additional tax each house will end up paying.
Click to expand...

Can you post a pic if possible. Not able to picture this
 
technofast said:
I too had this same problem with an older split a/c with the cooling not being maintained even after servicing. Later found out that it is due to the voltage fluctuation problem. The compressor does not start when there is low voltage or if the voltage fluctuates. The standard stabilizer does not boost the voltage. I had to buy a double booster stabilizer to overcome this voltage problem. Now it is working properly.
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mine is window one only. its not low voltage issue as it cant be low voltage since past 3 months daily right. it barely cools as cold as it did earlier
 
puns said:
Can you post a pic if possible. Not able to picture this
Click to expand...



blr_p said:
Can you post a pic i don't think i've ever seen such things before.
Click to expand...

This is like building a shed on your terrace with open sides. So pillars and roof frame made of hollow pipes and sheets on top of it. I would recommend steel sheets instead of cement sheets though. Cement sheets are very heavy and have less life as compared to steel sheets and they will be a PITA to get to the top floor because of the weight.
So basically it is a covered terrace so that sun rays don't directly hit the roof of the room.

Something like this -
images.jpg
 
rdst_1 said:
This is like building a shed on your terrace with open sides. So pillars and roof frame made of hollow pipes and sheets on top of it. I would recommend steel sheets instead of cement sheets though. Cement sheets are very heavy and have less life as compared to steel sheets and they will be a PITA to get to the top floor because of the weight.
So basically it is a covered terrace so that sun rays don't directly hit the roof of the room.

Something like this - View attachment 80503
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ok now i get it, i've seen people do this with tiles instead of sheets on top of the roof. They don't cover the entire roof though. That house made me think of a relatives and in the hot season was absolutely sweltering inside. The traditional way of dealing with this is opposing windows & doors to create a natural circulation inside. But people seem to have forgotten that simple principle these days.
 
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