# Central Air Conditioning Watts

How many watts are in a typical 3 ton central A/C unit, 5 ton unit and 10 unit? Does
Anyone know? I'm trying to figure out how much of my electricity bill is due to air conditioning and heating cost.

 hvac1000 Posts: 14,537, Reputation: 2381 Heating & Air Conditioning Expert #2 Aug 30, 2007, 04:04 PM

First you would have to figure your consumption of electric by the appliance. How many hours the unit has run and how many amps it takes it to run for one hour. Once you have those figures you can just use a amp to watts converter available on Google search.
 caibuadday Posts: 450, Reputation: 61 Full Member #3 Aug 30, 2007, 04:34 PM
Quote:
 Originally Posted by ken1972 How many watts are in a typical 3 ton central A/C unit, 5 ton unit and 10 unit? Does Anyone know? I'm trying to figure out how much of my electricity bill is due to air conditioning and heating cost.
you can't really tell, some like temp of about 72 but others like80, of course at72 it would cost more than 80, and it also depened on the outdoor temp..... I think the best way is let it run for about 5 min then take ampere, conversen it into watt then muptiply with the time it run( most stat now have run or filter time recording), and add that to the evap fan
 KISS Posts: 12,602, Reputation: 4378 Uber Member #4 Aug 30, 2007, 04:51 PM
You can estimate based on the data sheets.

An example:

2-1/2 Ton 208/230 Volt 1-Phase Scroll Compressor Direct Factory Replacement Part (Copeland): American HVAC Parts

Is a 2.5 ton compressor at 2.5 HP
You can assume a 1/3 HP outside blower and a 1/2 HP inside blower.
2.5 + 1/3 + 1/2 =3.33 HP

Running watts would be about 746*3.33 + 25 that 2486.8 W
Call it 2.5KW; there are 746 W/HP

At \$0.15/KWH it's about 2.5 KW * \$0.15/KWH = \$0.375/hr to operate

If it runs 5 hours per day 5 * 0.375 * 30 = \$31.75/month

Hopefully, my math is right. Running time could be off. Each month could be different because it depends on the cooling degree-days

Once you find a fudge-factor for degree-days, you might be able to get a seasonal cost.

USATODAY.com

Look at the nameplate for similar information.
 tkrussell Posts: 9,673, Reputation: 3698 Senior Electrical & Lighting Expert #5 Aug 30, 2007, 05:15 PM

One ton of refrigeration will equal approximately 3517 watts, so a 3 ton unit will draw 10551 watts. This is the load that is used to size service entrance calculations.

Assume the unit runs 5 out of 24 hours a day for one month:

150 hours x 10551 watts = 1582650/1000 = 1583 KWH @ \$0.15/KWH = \$237.45 per month.

Plug in your cost of a kilowatt-hour and the hours per day the unit runs and go from there. Should be close.
 hvac1000 Posts: 14,537, Reputation: 2381 Heating & Air Conditioning Expert #6 Aug 30, 2007, 06:11 PM

There are a lot of good answers here but the only way I found to satisfy my commercial customers years ago was to use a chart type recorder and calculate the exact amount of draw and at what temperature. For the average person buying these type of devices would be cost prohibitive. That is why I did not mention it in my first post. A/C equiptment draws a different amount of power depending upon how efficient it is and how hard it has to work to keep up with the outside temperature. On a cool day the a A/C unit might draw 20 amps but of a 100 degree day it might draw 22 amps. The condenser discharge temperature will be higher as the outside temperatures go up. The compressor has a harder time compressing the return gas into a higher pressure gas which in turn becomes a liquid in the condenser coils to start the cycle over by going back to the evaporator as a liquid to flash once again to a gas to pick up more work load from the inside of the home.
 ayeshaaakter1 Posts: 1, Reputation: 10 Junior Member #7 Feb 15, 2012, 12:34 PM
A central air conditioner is more than just the largest appliance in a homeâ€”itâ€™s part of a carefully designed system that also incorporates a thermostat and an array of ducts that deliver and circulate cooled air throughout the structure. In most cases, a central air-conditioning system is a more energy-efficient choice for regularly cooling a home than using room air conditioners in three or four different rooms.
However, thereâ€™s no getting around the fact that a central air conditioner can be fairly expensive to purchaseâ€”and that it must be installed by a qualified heating and cooling contractor. If your home doesnâ€™t have central air-conditioningâ€”but does have a network of ducts for a forced-air furnaceâ€”you likely can use the same ducts for cooling, as long as theyâ€™re the proper size and free of leaks and obstructions. On the other hand, if your home is heated by a boiler or electric baseboard units, youâ€™ll need to add a duct system, which can be both difficult and expensiveâ€”especially in a multi-level home, where you might have to sacrifice closet space or build â€śchasesâ€ť along walls or in corners to hold the ducts.
air conditioning
 lyme1966 Posts: 1, Reputation: 1 New Member #8 May 27, 2012, 10:46 AM
to second post kiss

5 x .375 x 30 = \$56.25
 wechslerl Posts: 2, Reputation: 1 New Member #9 Jun 14, 2012, 06:50 PM
Most of the answers here and elsewhere are between totally to partially wrong.
Do not mix horse power with cooling power.
A 5 ton a/c is the nominal capacity of a unit.
At 12,000 BTU per ton, a 5 ton will have close to 60,000 Btu (most of the time is 10% less)
At an Seer of 10 (1980 models) it will be 60,000/10=6.0Kw.
That's why we need the newer ones with SEER of 16 or higher.
60,000/16=3.750 kw+.675 fan=4.425 kw.
However in both examples the inside blower was not added to the total.
That inside Blower could vary between 1.0 to 1.7 kw, depending on the RPM and CFM

LW
 wechslerl Posts: 2, Reputation: 1 New Member #10 Jun 14, 2012, 07:04 PM
Continuation to the above post by LW
Today was a very, very hot day in Miami, 97 degrees.
Went outside to check if the dual stage compressor works as such.
I was surprised to see that on the newest Trane we just installed, the Amper-meter started with 14.5 Amps ans slowly climbed up to 18.5 Amps, this was compressor plus fan.
So if we take 57,500 Btu/16.0=3.593 kw (that's without the inside Blower).
Add inside Blower at 1.5Kw brings the total to about 5.093 kw.
At about 12 hours per day X 30 days X \$0.12/hr=\$220/month

LW

## Check out some similar questions!

Central air conditioning problem [ 2 Answers ]

My central air conditioning unit seems to work well with normal air flow. On several occasions at night the inside coil has frozen allowing little air to pass. I have reset the thermostat to a higher setting allowing the coil to thaw and air flow returns to normal. The daytime temps have been in...

Our central air conditioner would not start. Since we had this covered under our utility provider's WorryFree Services program, they sent a technician to look into the problem. The technician had to replace something like a transformer which had died due to old age. The airconditioner runs now...

Central Heat and Air not blowing air at all [ 1 Answers ]

Hello, I am a girl trying to save myself a little money and maybe embarrassment before I call someone out to look at my a/c problem. You know, trying to avoid the fact that I all I had to do was plug it in...ha/ha. I just moved into an apartment, everything was fine until all of a sudden I...

Air conditioning [ 1 Answers ]

Hi, I have a 4-wire Ritetemp thermostat, my wires are connected right but my unit on the outside will not come on. The blower comes on inside the house, but nothing outside. I not not have a pump. And there are no fuses to my unit outside. What do I do?

Air Conditioning [ 3 Answers ]

MY AC won't turn on.....................................