Central Air Conditioning vs window AC

[Stone]

If you see a house with a Central AC system and another similar size house with 3 window ACs, which house uses more electricity if the ACs are let run for the same duration? I am trying to compare Central AC vs Window ACs to see which one is more energy efficient. Thanks.

[Randy W]

Depends - the lower wattage systems use less electricity, but may need to run for a longer time to keep the temperature down. There is an optimum size.

 

Likewise, a unit that is too powerful may not kick in long enough to remove enough humidity.

 

The individual room units have the advantage that you can run only those in the rooms you are using.

[Sam and Fen]

I see that you live in MA so you will need heating in the winter.

 

When comparing costs also look if the Central AC units use a heat pump.

 

Heat pumps are much more efficient during the winter then oil/gas heat.

[dnoblett]

If you see a house with a Central AC system and another similar size house with 3 window ACs, which house uses more electricity if the ACs are let run for the same duration? I am trying to compare Central AC vs Window ACs to see which one is more energy efficient. Thanks.

 

An article: http://housewares.about.com/lw/Home-Garden...Conditioner.htm

[dnoblett]

I see that you live in MA so you will need heating in the winter.

 

When comparing costs also look if the Central AC units use a heat pump.

 

Heat pumps are much more efficient during the winter then oil/gas heat.

Beg to differ on the heat pump thing, not good in the NE, is hard to pump heat out of frozen air. Heat pumps are best in temperate zones like the middle and southern states, where the heat difference is not great.

 

I specified an AC unit for a server room a while back the company was confused in thinking I was going to use it as a heat pump, no dealer in this area carry heat pumps because they don't work when it is below freezing outside, I had to explain that I was pumping the heat OUT of the server room, and pumping the COLD from outside into the server room.

[Stone]

Thank you for your replies, Randy and Sam.

 

We are still in the process of shopping for a house in a nice area which we can also afford. It is getting so hot these days in MA, reaching 100 degree in many parts of MA yesterday. We see some houses with central AC, a nice feature, but my wife says central AC may cost a lot of energy than window AC.

 

In Massachusetts it is bitterly cold here, and most houses either use oil or gas furnaces to heat the houses in winters. I like window ACs, since they may use less energy. But in winters, it gets so cold here, that we may have to un-install all window ACs from windows for improved insulation. This un-installation process is inconvenient and the process could damage the AC extension wings like what happened to us.

[dnoblett]

Thank you for your replies, Randy and Sam.

 

We are still in the process of shopping for a house in a nice area which we can also afford. It is getting so hot these days in MA, reaching 100 degree in many parts of MA yesterday. We see some houses with central AC, a nice feature, but my wife says central AC may cost a lot of energy than window AC.

 

In Massachusetts it is bitterly cold here, and most houses either use oil or gas furnaces to heat the houses in winters. I like window ACs, since they may use less energy. But in winters, it gets so cold here, that we may have to un-install all window ACs from windows for improved insulation. This un-installation process is inconvenient and the process could damage the AC extension wings like what happened to us.

One option is AC units like you see in China, is called a ductless AC system, the unit has two parts, the indoor unit mounts high on the wall, and outdoor unit sits on a pad like central air, or can be hung on a wall, or sit on the roof, it uses a small hole to run the plumbing and electricity to the outdoor unit.

 

http://www.acsuperstore.com/Merchant2/graphics/00000001/PKAA12_18_lg.jpg

 

http://www.mehvac.com/

 

This is what I used to cool the server room.

 

 

 

Easy to install, and does not need to be removed for the winter.

[Stone]

If you see a house with a Central AC system and another similar size house with 3 window ACs, which house uses more electricity if the ACs are let run for the same duration? I am trying to compare Central AC vs Window ACs to see which one is more energy efficient. Thanks.

 

An article: http://housewares.about.com/lw/Home-Garden...Conditioner.htm

 

Thank you, Dan, for pointing to the article. The article does not say how much electricty a central AC systems uses as compared to window AC for the same running time. Apart from the one-time installation and purchase costs, I am not sure about the energy costs of the central AC.

[dnoblett]

From a Wikipedia post I found a heat pump is more efficient than electric heat until you get down to about freezing, then they are on par.

 

http://en.wikipedia.org/wiki/Heat_pump

 

I suspect gas heat costs less than a heat pump.

[HongKong2LA]

Another option is a cooling only mini-split (they do have heat pump models, but as mentioned, heat pumps are not that efficient in your local climate conditions). They mount on the wall so no need to remove them from the window in winter. The condenser would mount outside and they are small so they do not require a lot of room and the only wall penetration would be the refrigerant lines from the fan coil (indoor unit) to the condenser (outdoor unit). They sell like hotcakes in China, I'm sure you've probably seen thousands of them there but may not have noticed them. They are starting to catch on here in the US and you'll be seeing tons of them in the future.

 

http://www.coaire.com/Coaire/index.php?opt...=6&Itemid=3

Edited July 7, 2010 by HongKong2LA (see edit history)

[dnoblett]

Another option is a cooling only mini-split (they do have heat pump models, but as mentioned, heat pumps are not that efficient in your local climate conditions). They mount on the wall so no need to remove them from the window in winter. The condenser would mount outside and they are small so they do not require a lot of room and the only wall penetration would be the refrigerant lines from the fan coil (indoor unit) to the condenser (outdoor unit). They sell like hotcakes in China, I'm sure you've probably seen thousands of them there but may not have noticed them. They are starting to catch on here in the US and you'll be seeing tons of them in the future.

 

http://www.coaire.com/Coaire/index.php?opt...=6&Itemid=3

 

http://candleforlove.com/forums/index.php?...st&p=557538 Post #7

[HongKong2LA]

Another option is a cooling only mini-split (they do have heat pump models, but as mentioned, heat pumps are not that efficient in your local climate conditions). They mount on the wall so no need to remove them from the window in winter. The condenser would mount outside and they are small so they do not require a lot of room and the only wall penetration would be the refrigerant lines from the fan coil (indoor unit) to the condenser (outdoor unit). They sell like hotcakes in China, I'm sure you've probably seen thousands of them there but may not have noticed them. They are starting to catch on here in the US and you'll be seeing tons of them in the future.

 

http://www.coaire.com/Coaire/index.php?opt...=6&Itemid=3

 

http://candleforlove.com/forums/index.php?...st&p=557538 Post #7

 

oops..didn't see that...oh well, great minds and all that

[warpedbored]

I'm surprised no one has mentioned portable ACs. You still need to run a hose outside but it's a very easy uninstall if you make a simple window insert. The advantage is you can wheel it to the room you're using.

http://www.bestbuy.com/site/Air-Conditione...id=abcat0907004

[tonado]

Window AC is fine in Eastern MA since summer doesn't last long.

[tonado]

I'm surprised no one has mentioned portable ACs. You still need to run a hose outside but it's a very easy uninstall if you make a simple window insert. The advantage is you can wheel it to the room you're using.

http://www.bestbuy.com/site/Air-Conditione...id=abcat0907004

 

I was at Home Depots two years ago and the salesman said a lot of return on the portable ACs. A 10,000 BTU portable unit does not provide the same cooling as a 10,000 BTU window unit.