Solved

central air cheaper than traditional ways to heat/cooling?

Posted on 2010-08-27
13
384 Views
Last Modified: 2012-05-10
is central air very efficient and cost saving compared to traditional ways to heat/cool (example propane/windows AC) etc.

thanks
0
Comment
Question by:anushahanna
13 Comments
 
LVL 18

Accepted Solution

by:
Anil Golamari earned 56 total points
ID: 33542360
0
 
LVL 27

Assisted Solution

by:aburr
aburr earned 56 total points
ID: 33544107
I depends on what you want to do. If you just want to cool your living room a window air is good. If you want to cool a whole house central air is cheaper than buying a window unit for each room. Central air can be turned off for unused rooms)
Central air usually is for cooling only (although mine has a furnace built in)
Ground based heat exchangers often both heat and cool although they have not developed as large a market as conventional units.
0
 
LVL 32

Assisted Solution

by:aleghart
aleghart earned 276 total points
ID: 33544589
Window units (especially multiple units) have a problem with infiltration.  Not just the burglar who will pull it out to get into your house...   These units requires that you cut a hole into the wall or open a window for installation.  Whether it's running or not, you have infiltration of dust, bugs, moisture, and outside air.  A central air unit allows you to keep your windows closed.  The only openings in the wall would be for the condenser hose, control cable, and a condensate drip line.  These can all be sealed with foam and finished on the exterior so there is no infiltration of any kind.

Your home will heat up faster with a window unit because in addition to air infiltration, you've lost the insulation of double-pane windows in exchange for a hunk of metal, some plastic, and a sheet of plywood.  You can put foam all around...but that doesn't stop the heat from coming straight in.

>Central air usually is for cooling only

I don't know about that.  I see many houses here in southern California that have central heat, but no cooling.  Places like San Diego where it rarely gets into the 80s, but has plenty of breeze to cool the house.  They can have winter temps in the 40-50s, which require heating.
0
 
LVL 16

Assisted Solution

by:JohnBPrice
JohnBPrice earned 56 total points
ID: 33544999
>Central air usually is for cooling only

If depends upon your climate, central air (or sometimes window) heating units are known as "Heat pumps".  They work both ways and can either supply heating or cooling.  Heat pumps are more efficient than other heating systems if the outside temperature is over 40 F or so.  They often come with emergency electric heating units for the few occasions when the outside temp falls too low for the heat pump to keep up.  If your winter is colder and below 40 F most of the time, air heat pumps are not as efficient as gas or oil heat.

Geothermal heat (well, the most commonly found type anyway) is a heat pump which uses ground water instead of outside air to supply the heating/cooling.  They are extremely efficient because underground water is almost always over 50 F even in colder climates, and much cooler than the air in summer.
0
 
LVL 3

Assisted Solution

by:SantiagoA
SantiagoA earned 56 total points
ID: 33546043
Central units waist a lot of energy because they cool down (or heat up) the entire house all the time. Window units will work only in the rooms they are installed, so at night you only use energy to cool the bedroom while you sleep and save the electricity required to cool the rest of the house.
0
 
LVL 32

Assisted Solution

by:aleghart
aleghart earned 276 total points
ID: 33546175
^ That argument supposes a few things:

1. central air user does not want multiple rooms cooled
2. central air user does not close down dampers in unoccupied room
3. window unit is set to re-circulate room air.  Otherwise it's wasting energy converting 100F air.
4. window unit user does not mind noise of fans and condenser unit in the same room.

I have three bedrooms to cool.  Air recirculates automatically, drawing air from room-to-room.  The unit does not run 24/7.  Only when the temp falls out of range.

Window units typically run longer (or constantly), and run hot/cold.  Meaning, temperatures close to the unit are colder than desired, while the other side of the room is warmer than desired.

Central air can use a low-power recirculating fan to keep air moving at all times (better distribution) and much better filtration.

It's hard to do an apples-to-apples comparison.  They're designed for completely different uses.

Window units are (IMO) targeted to non-home-owners who have need for local cooling.  Meaning, the user is not concerned with infiltration, appearance, property value, multiple rooms.  This fits most all hotel rooms, apartments, dorm rooms, and users who like low entry costs for installing window AC units.

Like I said...totally different target markets.
0
Free Trending Threat Insights Every Day

Enhance your security with threat intelligence from the web. Get trending threat insights on hackers, exploits, and suspicious IP addresses delivered to your inbox with our free Cyber Daily.

 
LVL 6

Author Comment

by:anushahanna
ID: 33559865
Thanks for the different aspects of looking at it.

In terms of strict cost of producing coolness in summer, let's say there are 4 rooms in 2 homes. First home uses Centrail Air to cool all 4 rooms 24/7. The other home uses 4 windows units to cool 24/7. Which one will have lighter electric bill?

my bigger question is- is there any technological advance in the central air to keep the electric cost to a lower level?

thanks
0
 
LVL 32

Assisted Solution

by:aleghart
aleghart earned 276 total points
ID: 33560598
Central air will be more efficient for cooling all the rooms.  You would hand 4x 10,000 or 12,000 Btu window units.   Whereas a 3-ton unit cools my entire house (3BR, LR, DR, Kitch, 1BA cooled, 1BA no vent).

With window units, you'll have to overcool the rooms for it to reach hallway or common areas, or usually accept that the cool area doesn't extend past the room.  Too keep cold air in one room cool (adjacent areas not trading warm air into it), you'll typically close the doors.

IMO, window units aren't a good whole-house solution. Besides the inefficiency aspects, there are health issues.  Respiratory problems from the inevitable mold, stale air from closing doors, infiltration of dirt and allergens every time you mow the grass, etc.  I rented a house where that was the only solution available...plywood and a window unit.  I was very happy when we left.  Summers were unbearable, as the solution was to live in the bedroom or leave the house.  That's not a home...it's just a rented bed and a place to store your stuff.

Some houses fare better.  In SoCal, summers hit 95-100+ on bad days.  On "good" days, it's 80-85.  That's sufficient to bake unconditioned houses to upwards of 88F inside unless A/C is running to keep the temps down.  With proper shade, breezes, and a cooler outside environment, you could get by with a window unit or two.

I know, there are plenty of people who think that A/C is unnecessary.  My grandparents were from the Depression, and the first thing they did was install a window unit as soon as they could afford it.  It kept getting bigger every year until they finally sprung for a central unit.  Grandma's still frugal about when it comes on, and hand is smacked if you touch the thermostat...but it made more sense to spend money on a whole-house solution rather than spend the same amount of money on electricity for a giant window unit.  Then, spend more money heating the house in winter because of the giant hole in the wall protected by a garbage bag over the window unit.

That's the other downside of window units.  Infiltration in the wintertime increases your heating bill, even if you do wrap the unit with a garbage bag.  I like closing the windows with central air, and not hearing any outside noises or feel the drafts.

It's not for everyone, but definite advantages.
0
 
LVL 6

Author Comment

by:anushahanna
ID: 33560758
that are great points. Thanks for your story of grandma, too. definitely, central air has lots of benefits.

what is the proportion of 12,000 Btu to 3 ton central air, in terms of electricity that will be drawn(consumed), for let's say, 24 hours straight. i am also looking for apple to apple, cents to cents comparison, of how the technology fares with each other, in terms of costs.
0
 
LVL 32

Assisted Solution

by:aleghart
aleghart earned 276 total points
ID: 33561181
It depends a lot on efficiency of the units.  Window units (in general) are already less efficient.  But, new central units are far better than the older units like I have at my house.

Here's a power cost estimator for central AC units.  It's an Excel spreadsheet requiring user input:
http://www.energystar.gov/ia/business/bulk_purchasing/bpsavings_calc/Calc_CAC.xls

Here is similar for "room" unit.  Not sure if that means window or in-room unit with exhaust:
http://www.energystar.gov/ia/business/bulk_purchasing/bpsavings_calc/CalculatorBulkPurchasingRoomAC.xls

Don't forget the benefits of programming.  Whether it's window or central, being able to set thermostat and on/off cycles throughout the day are the best way to get comfort cooling.  For instance, I never let the house get above of 84 (M-F) and 64-77 (Sa-Sn).  Then bring the temp down to 76F at 4pm to have the house cool when we get home.  Same goes for winter...never let the house get below 60, then up to 70 at 4pm, 68 at 10pm.
0
 
LVL 6

Author Comment

by:anushahanna
ID: 33580453
OK. So you would not be surprised if someone using 2 window units occationally have a bigger elec bill than someone running central air for longer time period, necessarily, right?
0
 
LVL 32

Assisted Solution

by:aleghart
aleghart earned 276 total points
ID: 33581075
Wouldn't be surprised if it happened occasionally.  If they're only used for a couple of hours per day, then the window units might consume less electricity.  That's what makes them good for apartments and hotels...the rooms are more often empty and unused.

But, for the same amount of cooling (volume, temperature, time, etc.) I would guess that a newer (14+ SEER) central unit would outperform window units in terms of comfort and electricity consumption.
0
 
LVL 6

Author Comment

by:anushahanna
ID: 33586017
Thanks very much for your detailed help and input, aleghart.
0

Featured Post

Do You Know the 4 Main Threat Actor Types?

Do you know the main threat actor types? Most attackers fall into one of four categories, each with their own favored tactics, techniques, and procedures.

Join & Write a Comment

Lithium-ion batteries area cornerstone of today's portable electronic devices, and even though they are relied upon heavily, their chemistry and origin are not of common knowledge. This article is about a device on which every smartphone, laptop, an…
If you get continual lockouts after changing your Active Directory password, there are several possible reasons.  Two of the most common are using other devices to access your email and stored passwords in the credential manager of windows.
Notifications on Experts Exchange help you keep track of your activity and updates in one place. Watch this video to learn how to use them on the site to quickly access the content that matters to you.
Articles on a wide range of technology and professional topics are available on Experts Exchange. These resources are written by members, for members, and can be written about any topic you feel passionate about. Learn how to best write an article t…

746 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

15 Experts available now in Live!

Get 1:1 Help Now