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Old 12-08-2009, 01:04 PM   #11
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Good point!
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Old 12-08-2009, 01:08 PM   #12
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Wow! Very impressive calculations. I'm surprised to learn that electric is cheaper. Given the amount of coal burned for electricity, I imagine the gas appliances are more environmentally sound. And more efficient where gas is used for electricity, because energy is always lost in the process of conversion.

What's your experience with the noise level of the gas refrigerator? I keep my home quiet enough that the hum of the electric 'fridge is really noticeable. Well, until the dogs start barking, that is.
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Old 12-08-2009, 01:19 PM   #13
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Hi Jenny!

Well, the numbers are right IF calculating them the way I did is correct

As for noise - the gas refrigerators make NO noise, as they have no moving parts to make noise (or wear out).
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Old 12-08-2009, 01:22 PM   #14
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Well, that's a major point in their favor as far as I'm concerned, then.
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Old 12-08-2009, 01:27 PM   #15
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The only real problem with the modern-built absorption refrigerators is that they're not built as well as the old Servel's. As a result, their a little uglier (something most folks could probably live with), and, if not setup right, they can develop leaks in the cooling system after several years.

The upside is that there are many companies out there now who service the modern cooling units (whereas it's harder to find folks who work on the older ones, but they DO exist), and you can send it in directly if it's out of warranty, saving you the expense of paying someone else a markup to do it for you.
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Old 12-09-2009, 03:41 PM   #16
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Hello all!

Well, I finally got some definitive answers from the local natural gas company, the people at Crystal Cold, and the local propane people. What follows is a summation of that information. I apologize for posting this again (sort of), but I couldn't figure out how to go back and edit the earlier posting with the other numbers.

I believe these numbers are correct.

Oh - and I want to point out: the reason you can't just take the number BTU's the gas refrigerators are rated at and derive the cost of use is because these things vary in how much they use per hour. The variable in this equation is the flame on the burner - they do not use the full BTU's their rated at per hour. Instead, they operate at that rate when the flame is at it's high position when the thermostat is calling for more cooling, and at a lower level when "idling". Thus, the rate of gas use is calculated per day, not per hour.

That said, the Crystal Cold 12 cubic foot refrigerator, according to the manufacturer, uses .28 gallons of LPG per day, and the 18 cf unit uses .35 gallons per day.

Now - there are 91,600 BTU's per gallon of LP gas.

91,600 x .28 = 25,648, so the 12 cf unit uses 25,648 BTU's per day, and the 18 cf unit uses 32,060 BTU's per month (91,600 x .35).

So - in a month, the 12 cf unit would use 8.4 gallons of LPG (30 x .28 gallons), which equals 769,440 BTU's per month (25,648 x 30), and the 18 cf unit would use 10.5 gallons of LPG (30 x .35 gallons), which equals 961,800 BTU's (32,060 x 30) in a month.

Currently, LP Gas here now costs $2.24 per gallon. That means the 12 cf unit costs $18.82 per month to operate on LPG and the 18 cf unit costs $23.52 per month to run on LPG. Simply put, the two refrigerators cost $0.63 and $0.78 per day to operate on LPG, respectively.

Now, converting over to natural gas -

There are 1,000,000 BTU's in a DekaTherm. We take the daily BTU usage of our two refrigerators, divide them into 1,000,000, and we get the number of days they will operate on 1 DkT of natural gas:

* 12 cf unit will operate for 39 days on 1DkT of natural gas.
* 18 cf unit will operate for 31.19 days on 1DkT of natural gas

The local natural gas company charges, including ALL charges, delivery fees, etc., $17.67 per 1,000,000 BTU's (1 DekaTherm) of natural gas (I finally got them to tell how much they REALLY charge).

That means the 12 cf unit will run for 39 days for $17.67, or $0.45 per day, and the 18 cf unit will run for 31.19 days for the same amount of money, which equals $0.57 per day.

Now let's look at my old Servel Model 856G, made in 1955 -

According to the experts, it uses about 2.2 pounds of propane per day. The Crystal Cold 12 cf unit, which is similar in size, uses 1.2 pounds per day, which is the equivalent of .28 gallons of propane.

There are 4.24 pounds of propane in a gallon. One gallon of propane = 91,600 BTU's, so my older Servel uses 47,528 BTU's per day (91,600 divided by 4.24 x 2.2), which is close to the number you get when you divide 2.2 by 1.2 (1.83) and multiply it by the number of BTU's the 12 cf Crystal Cold unit uses in a day (25,648) = 46,936 BTU/day.

So, the older Servel uses, let's say, 47,000 BTU's per day. That means, in a month, it will use 1,410,000 BTU's, which equals 15.39 gallons of LPG per month (1,410,000 divided by 91,600), which means it costs $34.47 (15.39 x $2.24) per month to operate it on LPG, or $1.15 per day.

Using natural gas, the old Servel gets 21.28 days per DekaTherm (1,000,000 divided by 47,000), which, at $17.67/DkT = $0.83 per day to run on natural gas ($17.67 divided by 21.28).

Now - I also was able to get our electric company to tell me what the electricity REALLY costs per kwh, including their "service fee", which is $13 per month, which is $0.43 per day.

That means -

General Electric's GTR12HBXRWW 12 cubic foot electric refrigerator uses 1.13 kwh per day to run. 1.13 X $0.084 + $0.43 (the daily base cost) = $0.52 per day.

General Electric's GTS18IBRBB 18 cubic foot electric refrigerator requires, they say, 478 kwh per year to operate, which is 1.30 kwh per day to run. 1.3 X $0.084 + $0.43 = $0.54 per day.

According to Cornell University http://www.human.cornell.edu/che/DEA/outreach/upload/Refrigerator_Replace.pdf), GE is probably "right in there" with their numbers.


Now that we have the correct numbers, here's the -

Bottom Line:

* The 12 cf unit costs $0.63 per day to operate on LP gas, and $0.45 per day on natural gas.
* The 18 cf unit costs $0.78 per day to operate on LP gas, and $0.57 per day to operate on natural gas.
* The older Servel, like mine, costs $1.15 per day to operate on LP gas, and $0.83 per day on natural gas.
* GE's 12 cf electric unit costs $0.52 per day to operate, and
* GE's 18 cf electric unit costs $0.54 per day to run.


Hope this helps someone. Thanks for being patient while I got the numbers right - I didn't realize there would be so many differing ideas on how to calculate these things, but I think we're there now.

But - if I made any errors, PLEASE let me know!

Todd W. White

Last edited by VintageServel; 12-10-2009 at 12:18 PM. Reason: Got updated numbers from the electric company & made corrections to the calculations accordingly.
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