Tenancy Agreement: Limit on aircon usage

[zzm9980]

She said: What about turning on both the fan and the ac (on high setting) simultaneously? It uses less electricity than relying on the ac alone?Typically people do not distinguish functional devices inside the AC

You're right. So are we now saying Earthfriendly was talking about the fan inside the a/c unit? or a standalone?

Either way, this tangent has gotten stupid.

I'm curious what 'too expensive' is anyway now. In our unit (3 room HDB rental), my SP Power bill was ~115-120 a month with almost no aircon. Now I use it every night when we go to bed for 6-8 hours. The bill is about $25-30 higher a month, so slightly less than $1 a night.

[x9200]

Zzm, I think you know what she was talking about at least in respect of the fans. Admittedly, after she posted the links I did not know any longer if I understood her right but what she wrote was correct as per my understanding

For the bill, hard to say, but if AC runs at low temperature settings in a bigger room I think it may be more than this dollar a day.

[Wd40]

We always keep the aircon temperature at 27 and then turn on the table fan too. We don't use the thick blankets that normally people use, but rather thin fabric ones.

My logic is, setting the aircon at 22 or 24 and then using thick blankets totally defeats the purpose.

Also some people say they initially set the aircon to 17 and then after 2 hours switch it off. I don't agree with this concept too.

The reason we keep the fan also on and in rotating mode so that everyone gets the airflow and not just the person sleeping below the aircon.

I don't subscribe to zzm theory that keeping 2 devices on is worse. In our case we are relying not just on temperature setting but airflow too. Using only temperature setting will need you to set it at 22 and then use think blankets, which will consume more power as the aircon need ps to work harder to maintain the temperature at 22 compared to 27 which is just 3 degrees below room temperature.

Call me a cheapo Asian, but I call it efficient usage of resources

[Sergei82]

...will consume more power as the aircon need ps to work harder to maintain the temperature at 22 compared to 27 which is just 3 degrees below room temperature.

Why I always thought that it is the aircon being on or off that matters the most? Setting it to any temperature - lower/higher - will not make any visible difference in your electricity bill. At least that is what I was told by a technician to came to my place to verify the meter.

[zzm9980]

My logic is, setting the aircon at 22 or 24 and then using thick blankets totally defeats the purpose.

If you grew up in a temperate climate and 'bundled' in blankets most of your life, you'd likely find it much easier to sleep like this.

I don't subscribe to zzm theory that keeping 2 devices on is worse.

I didn't say it was worse. I said using two devices at the same time is more electricity than just one device at the same time. EF made no distinction about relative comfort for a person or any other subjective measurement; she simply said a fan and A/C on at the same time will use less electricity than just an A/C.

I even found a nice meme that applies:

[zzm9980]

...will consume more power as the aircon need ps to work harder to maintain the temperature at 22 compared to 27 which is just 3 degrees below room temperature.

Why I always thought that it is the aircon being on or off that matters the most? Setting it to any temperature - lower/higher - will not make any visible difference in your electricity bill. At least that is what I was told by a technician to came to my place to verify the meter.

Yes, that is what I also know, but didn't want to bother arguing that point here now. The compressor is on or off. It turns on when you turn it on, it turns off when it reaches the temperature you set it to. x92's point is the secondary room fan will in theory help the cooler air reach the thermostat sooner for a more accurate reading, perhaps allowing the A/C compressor to turn off sooner. Or perhaps in an inefficiently insulated room, it will help the cooled air to escape faster. Too many variables to say for sure, which is why I stick with my original fact: All other things being equal, turning on two devices will always use more electricity than just turning on one of the two.

[x9200]

...will consume more power as the aircon need ps to work harder to maintain the temperature at 22 compared to 27 which is just 3 degrees below room temperature.

Why I always thought that it is the aircon being on or off that matters the most? Setting it to any temperature - lower/higher - will not make any visible difference in your electricity bill. At least that is what I was told by a technician to came to my place to verify the meter.

Sorry, I can not find more straight forward data so you have to calculate the fractions by yourself and this is for a central AC not some wall mounted domestic one:



Power consumption at 27 is ~245kWh; at 22 is ~300kWh this is ~20% of the difference. There are many people using AC 24/7 with their total bills reaching 0.6-0.7k of which AC is like 0.4-0.5k.

[zzm9980]

...will consume more power as the aircon need ps to work harder to maintain the temperature at 22 compared to 27 which is just 3 degrees below room temperature.

Why I always thought that it is the aircon being on or off that matters the most? Setting it to any temperature - lower/higher - will not make any visible difference in your electricity bill. At least that is what I was told by a technician to came to my place to verify the meter.

Sorry, I can not find more straight forward data so you have to calculate the fractions by yourself and this is for a central AC not some wall mounted domestic one:



Power consumption at 27 is ~245kWh; at 22 is ~300kWh this is ~20% of the difference. There are many people using AC 24/7 with their total bills reaching 0.6-0.7k of which AC is like 0.4-0.5k.

Your chart says kW not kWh. Either you misinterpreted it, or there is a typo. Without knowing definitely which is right, it either proves you or Sergei. It's obvious the longer an AC runs the more power it will use. The floor fan in conjunction may or may not help this. For all you know, EF's floor fan is pointed towards a rickety window and not the thermostat.

[x9200]

What difference does it make whether it is kW or kWh? Do you expect time to run differently in different places with some statistical significance? It is still 20% less or more. I think I will give up at this point.

[Wd40]

...will consume more power as the aircon need ps to work harder to maintain the temperature at 22 compared to 27 which is just 3 degrees below room temperature.

Why I always thought that it is the aircon being on or off that matters the most? Setting it to any temperature - lower/higher - will not make any visible difference in your electricity bill. At least that is what I was told by a technician to came to my place to verify the meter.

Have you ever driven a manual transmission car, with aircon? Have you noticed the visible difference in pickup when the aircon thermostat cuts in and off?

Its not the temperature setting directly that matters. Its whether thermostat is in cut in mode or cut off mode. When it is in cut in mode the compressor is working and it is cooling the room gradually until the desired temperature is reached, after that the thermostat cuts off and then it is not working and hence not consuming the same amount of electricity.

The lower the temperature you set, the longer the thermostat needs to be in cut in mode.

If you really want to prove it, you can do this:

Turn your aircon on and set it to high temperature like 35 and then go out and see your electricity meter disc rotation speed. After that set it to a temperature below the current room temperature and then go and see the rotation speed.

[zzm9980]

What difference does it make whether it is kW or kWh? Do you expect time to run differently in different places with some statistical significance? It is still 20% less or more. I think I will give up at this point.

Power consumption at 27 is ~245kWh; at 22 is ~300kWh

I read the graph as you use 300kW of power to reach 22c, but only 245kW to reach 27c. No where does the graph indicate the time is constant between those two. It runs 20% longer, uses more power overall.

[x9200]

What difference does it make whether it is kW or kWh? Do you expect time to run differently in different places with some statistical significance? It is still 20% less or more. I think I will give up at this point.

Power consumption at 27 is ~245kWh; at 22 is ~300kWh

I read the graph as you use 300kW of power to reach 22c, but only 245kW to reach 27c. No where does the graph indicate the time is constant between those two. It runs 20% longer, uses more power overall.

This graph makes only sense if you assume the power expenditure is measured at equilibrium condition so you set the AC to 22 deg and wait till it reaches 22 and remains constant at this temperature (within allowed variation). At that point you start measuring the power consumption over some period of time. Same for the higher temperature setting.

[Strong Eagle]

Wd40 is correct. Setting the thermostat to lower temperatures cause the compressor to run longer to reach those temperatures which in turn raises electricity costs.

[iamsen]

With the power crunch in Japan, several restaurants have resorted to installing ceiling fans and running them together with the AC.

I don't remember the exact numbers anymore but the AC running at 26 degree (govt. recommended settings for summer) is several times more efficient than one set at 22 degrees. Every 1 degree consumes a significantly larger amount of power, more than what a fan set at maximum will consume.

The ceiling fans helps the cool air circulate the premise, reducing discomfort (26 deg. AC in summer is not comfortable), and reaps significant power savings compared to having the AC set at <24 deg the whole time.

[iamsen]

http://www.thesimpledollar.com/2012/06/ ... in-166365/

Closest article I could find with actual kwH and $.