Chillers: Are they really that expensive to run?

lunarlanderboy · 03/21/2008, 07:32 PM

I think I might be doing this calculation wrong because when I figure out how much a 1/10 hp chiller costs to run 12 hours a day for a year the cost only comes out to like $25 - if a chiller pulls 1/10 of a horsepower and a horsepower is around 746 watts, a 1/10 is like 75 watts. So would a 1/10hp chiller pull the same electricity as a 75 watt light while it is running? I must be missing something because that's not very expensive.

BeanAnimal · 03/21/2008, 08:24 PM

A 1/10 HP chiller uses about 250 watts.

12 hours a day is 3kWh per day or 1095 kWh per year or $164 if you pay .15 per kWh.

lunarlanderboy · 03/21/2008, 08:47 PM

thanks! That makes more sense - why are they called 1/10 horsepower then? - out of curiosity - Luckily I pay 0.09 per KWH in Phoenix, AZ

BeanAnimal · 03/21/2008, 09:52 PM

Honestly? Because that is the label that the OEM decided to put on that particular size of chiller. It is common for the chilling capacity to be rated in HP or Tons of A/C, but even those number are more than a little misleading. It is NOT very common to rate the power consumption of the unit.

In the chiller article in my website ( www.beananimal.com ) I give a little bit of history about where the unit come from. You also google "ton of air conditioning" and get a lot more information.

lunarlanderboy · 03/21/2008, 10:33 PM

thanks! That makes more sense - why are they called 1/10 horsepower then? - out of curiosity - Luckily I pay 0.09 per KWH in Phoenix, AZ

lunarlanderboy · 03/22/2008, 01:01 PM

Thanks for the info Bean Animal!

BeanAnimal · 03/22/2008, 01:32 PM

No problem

Lewin · 03/22/2008, 04:52 PM

I never noticed any appreciable difference in my electric bill when I added a chiller. Also it isn't like your lights which are on all day. The chiller cycles on and off as needed. I have never had it run continously for more than 20 minutes.

BeanAnimal · 03/22/2008, 05:11 PM

Lewin, it all depends on the heat load and the capacity of the chiller.

Lets say that 1/10 HP chiller moves around 1200 BTU/h and you put it on a 50 gallon tank (416 pounds of water). Lets say without the chiller the tank rises from 80 egress to 85 degrees in 4 hours. Lets also say that the hot part of the day is 10 hours.

We know that it takes 1 BTU to raise (cool) 1 pound of water 1 degree Fahrenheit. So in that 4 hours that tank gains 2080 BTUs of energy that a chiller needs to remove or 520 BTU/h. We also know that over the 10 hours the heat load stays about the chiller will have to remove 5200 BTUs over the 10 hour period.

So the chiller moves 1200 BTU/h. That means that the chiller must run for about 26 minutes every hour to keep that temperature at 80 degrees. So 260 minutes a day is our working number.

260 minutes @ 250 Watts is 1.1 kWh per day.

So at $.15 per kWh it costs maybe 17 cents a day for that chiller.

We can do the same math for a 1/2HP chiller and a 150 gallon tank with a 10 degree temp rise. You will find that the costs can become rather significant (easily $1-5$ a day depending heat load and tank size)

Bean

03/21/2008, 07:32 PM	#1
lunarlanderboy Premium Member Join Date: May 2003 Location: Novato (Bay Area), CA Posts: 573	Chillers: Are they really that expensive to run? I think I might be doing this calculation wrong because when I figure out how much a 1/10 hp chiller costs to run 12 hours a day for a year the cost only comes out to like $25 - if a chiller pulls 1/10 of a horsepower and a horsepower is around 746 watts, a 1/10 is like 75 watts. So would a 1/10hp chiller pull the same electricity as a 75 watt light while it is running? I must be missing something because that's not very expensive. __________________ *** Current Tank Info: 40 gallon glass cube with 40 gallon breeder sump, 250 watt 14K MH, MSX 160 skimmer

03/21/2008, 08:47 PM	#3
lunarlanderboy Premium Member Join Date: May 2003 Location: Novato (Bay Area), CA Posts: 573	thanks! That makes more sense - why are they called 1/10 horsepower then? - out of curiosity - Luckily I pay 0.09 per KWH in Phoenix, AZ __________________ *** Current Tank Info: 40 gallon glass cube with 40 gallon breeder sump, 250 watt 14K MH, MSX 160 skimmer

03/21/2008, 10:33 PM	#5
lunarlanderboy Premium Member Join Date: May 2003 Location: Novato (Bay Area), CA Posts: 573	thanks! That makes more sense - why are they called 1/10 horsepower then? - out of curiosity - Luckily I pay 0.09 per KWH in Phoenix, AZ __________________ *** Current Tank Info: 40 gallon glass cube with 40 gallon breeder sump, 250 watt 14K MH, MSX 160 skimmer

03/22/2008, 01:01 PM	#6
lunarlanderboy Premium Member Join Date: May 2003 Location: Novato (Bay Area), CA Posts: 573	Thanks for the info Bean Animal! __________________ *** Current Tank Info: 40 gallon glass cube with 40 gallon breeder sump, 250 watt 14K MH, MSX 160 skimmer

03/21/2008, 08:24 PM	#2
BeanAnimal Registered Member Join Date: Feb 2003 Location: Pittsburgh Posts: 20,772	A 1/10 HP chiller uses about 250 watts. 12 hours a day is 3kWh per day or 1095 kWh per year or $164 if you pay .15 per kWh.

03/21/2008, 09:52 PM	#4
BeanAnimal Registered Member Join Date: Feb 2003 Location: Pittsburgh Posts: 20,772	Honestly? Because that is the label that the OEM decided to put on that particular size of chiller. It is common for the chilling capacity to be rated in HP or Tons of A/C, but even those number are more than a little misleading. It is NOT very common to rate the power consumption of the unit. In the chiller article in my website ( www.beananimal.com ) I give a little bit of history about where the unit come from. You also google "ton of air conditioning" and get a lot more information.

03/22/2008, 01:32 PM	#7
BeanAnimal Registered Member Join Date: Feb 2003 Location: Pittsburgh Posts: 20,772	No problem

03/22/2008, 04:52 PM	#8
Lewin Registered Member Join Date: Sep 2001 Location: Costa Mesa, California Posts: 104	I never noticed any appreciable difference in my electric bill when I added a chiller. Also it isn't like your lights which are on all day. The chiller cycles on and off as needed. I have never had it run continously for more than 20 minutes.

03/22/2008, 05:11 PM	#9
BeanAnimal Registered Member Join Date: Feb 2003 Location: Pittsburgh Posts: 20,772	Lewin, it all depends on the heat load and the capacity of the chiller. Lets say that 1/10 HP chiller moves around 1200 BTU/h and you put it on a 50 gallon tank (416 pounds of water). Lets say without the chiller the tank rises from 80 egress to 85 degrees in 4 hours. Lets also say that the hot part of the day is 10 hours. We know that it takes 1 BTU to raise (cool) 1 pound of water 1 degree Fahrenheit. So in that 4 hours that tank gains 2080 BTUs of energy that a chiller needs to remove or 520 BTU/h. We also know that over the 10 hours the heat load stays about the chiller will have to remove 5200 BTUs over the 10 hour period. So the chiller moves 1200 BTU/h. That means that the chiller must run for about 26 minutes every hour to keep that temperature at 80 degrees. So 260 minutes a day is our working number. 260 minutes @ 250 Watts is 1.1 kWh per day. So at $.15 per kWh it costs maybe 17 cents a day for that chiller. We can do the same math for a 1/2HP chiller and a 150 gallon tank with a 10 degree temp rise. You will find that the costs can become rather significant (easily $1-5$ a day depending heat load and tank size) Bean