Window Aircon - Switch off or leave it running at a higher temp

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superczar

superczar

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Chennai is getting crazy hot, all the more so with all the humidity here

Now I usually switch on the living room Aircon after coming back from work, then switch if off and switch on the BR AC just before crashing

and if I am stepping out of the house for 10 mins or more, I switch em off

Now am wondering how efficient/inefficient would it be to leave at least the living room unit on (in powersave mode) at a relatively higher temp setting if I am going to be out for an hour or two (or more)

Since when I switch on the unit after returning, the compressor works non-stop for a long while to get the room cool, and if I switch it off for an hour, it has to start from scratch again

Wouldn't it be more (or at least equally) efficient (and certainly a lot more convenient) to just raise the temperature (say 29 C) , enable power save mode and leave it on ...If not all day long, at least as long as I am home?
 
It depends on how well insulated your room is. In my uncles place in Texas, he left the central aircon on at a higher temp even when we went on a week long road trip. He said he had compared an electricity bill to when he had turned it off in a similar situation, and it was lower when he left it on. Then again, the houses there are designed to be well insulated, and im not sure how much builders here take that into account. The best thing to do is do a test during electricity billing cycles. The weather should be pretty consistent for the next 4 months (minus the few days we may get some of the southwestern drizzles). So if you have some disposable income, go ahead and try it out.
 
You cant really say that this month bill is higher by Rs500-1000 cuz of this particular factor. Its difficult to do apportionment of an electricity bill cuz

Rs500-1k variation is normal.

I remember at the back of my electricity bill it said a 1.5ton A/c consumes 2units/hour.

Cost/unit for the first 200units is Rs2.40, for the next 200units is Rs.3.90, and above 400units is Rs.4.60

So I think its okay to leave it on for like 1-2hours max.

If you really wanna see how much bijli ur aircon is consuming, switch off everthing in ur house, turn on that a/c and go stand next to ur electricity meter and measure the time it takes to consume one unit
 
since the electricity meter is right downstairs, i can easily run a check against that..but then I do not intend to leave it on during the days (say from 11-7) when no one is at home..

and the variability is too high for the rest of the time
 
btw whats the max temp for the day there in chennai?

It was ~46*C max here today, though some newschannel were claiming 48*c
 
one more recommendation. open all the doors windows of that room and any door which may result in a better airflow. Once you feel that the room has been well ventilated, only then switch on the AC and not directly after that.
 
Well, some years ago, I had a health issue which required keeping the AC on 24 hours a day for a month. Turns out the bill was no higher than keeping it on for 5 hours a day. This is because the AC was rarely actually running since the moment the temperature started rising, it would wake up for 10 minutes and push it back down.
 
Well, some years ago, I had a health issue which required keeping the AC on 24 hours a day for a month. Turns out the bill was no higher than keeping it on for 5 hours a day. This is because the AC was rarely actually running since the moment the temperature started rising, it would wake up for 10 minutes and push it back down.
Click to expand...

Thanks for this...

so let me take my chances, and leave the damned thing running at least for this cycle for starters

btw whats the max temp for the day there in chennai?

It was ~46*C max here today, though some newschannel were claiming 48*c
Click to expand...

It's hovering in the high 30s but the 80% + humidity is pushing the heat index (what you feel) is hovering between 43-48 with Wednesday predicted to feel like 49 C
 
OT, but could you please tell me what ur electricity bill was before installation and after installation of the AC? I'm seriously considering getting one myself, bangalore heat n humidity is getting insane..
 
Here's my take on this question. Like Grease Monk said, it all depends on how well your room under test (RUT) is insulated. If the insulation is very good, you should know by this test. If you had the AC running and turned it off while you stepped out for an hour, is the room still comfortably cool when you return?

Note that the term comfortably cool encompasses both temperature and humidity.

If yes, then i feel it would hardly matter whether the AC was left on or turned off.

On the other hand, if the RUT has become uncomfortable, it means that it is poorly insulated. In such a case, leaving your AC on while you are out might give a little more comfort to a neighbour to where your cool air is leaking but will certainly result in increased bills.

For an intuitive analysis you will realize that the loss of energy is proportional to temperature difference and hence making your AC work to maintain a higher differential will intuitively result in higher energy loss during that period.
 
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