Quantcast
Propane refrigerator - Homesteading Today
Homesteading Today

Come enter the Lehman's Aladdin Lamp Giveaway - Last Day to Enter!

Go Back   Homesteading Today > General Homesteading Forums > Homesteading Questions


Reply
 
LinkBack Thread Tools Rate Thread
  #1  
Old 11/09/09, 07:28 PM
 
Join Date: Nov 2002
Location: Alaska
Posts: 4,527
Propane refrigerator

Didn't want to hijack the "no elec" thread so I'll start another question. For those who have used them, what should one look for in a propane fridge? Where is the best place to get them? Brands? Where do you even look to find reviews? We are currently off-grid. The system is managing the fridge at the moment but it is a power hog and it would be nice not to have to watch our watts quite so closely. We've got a lot to consider, including a more efficient elec model and upgrades to our power system, but having info about the propane fridge would be a handy input to the equations. Reality is that DH would like to run a TV. Thanks in advance for any help!

Reply With Quote
  #2  
Old 11/10/09, 06:11 AM
 
Join Date: Jan 2005
Location: Florida
Posts: 4,475

Dometic and Norcold are probably the two most common brands.

Propane refrigerators cool down much more slowly than a compressor refrigerator. You don't want to put a lot of warm stuff in it at one time. They work better at keeping it cool than they do at cooling it down.

I haven't checked reviews, but I'm sure you can find a ton of stuff on a Google search.

You can get them from RV dealers and Lehman's (www.lehmans.com) carries them. You can probably find other on line dealers that have them as well.

__________________
Reply With Quote
  #3  
Old 11/10/09, 06:37 AM
7thswan's Avatar
 
Join Date: Nov 2008
Location: michigan
Posts: 18,298

Servall (sp)

__________________
Reply With Quote
  #4  
Old 11/10/09, 07:01 AM
 
Join Date: Jan 2004
Location: WI
Posts: 2,180

Back in the mid1980s when propane was cheap and PVs were expensive, we spent the money (nearly $2000) on a 12 cu ft Sunfrost 12 volt refrigerator to replace our old Servel propane fridge. We figured that the savings in propane over the life of the refrigerator would pay the cost of the refrigerator and the PVs needed to run it. The refrigerator and the PVs are still working properly, over 2 decades later, so we feel that we made the right choice, especially considering the cost of propane today.

Get more PVs and get an energy efficient electric refrigerator. Another benefit is no gas fumes in the house from the refrigerator.

__________________
Reply With Quote
  #5  
Old 11/10/09, 07:13 AM
 
Join Date: Aug 2009
Location: NC
Posts: 1,352

RV, travel trailer salvage yards are good places to find the dual fuel (110V/propane) refrigerators at a good price. Mine came from a travel trailer that had been wrecked.

Also, consider buying a used travel trailer to strip it of all the components that are useful in living off the grid. This time of year, people are more likely to get rid of them because they don't want to spend money to store them over the winter. The cost of the whole unit can be much less than buying the applicable components separately.

Dual fuel refrigerator
12v water pump
Propane furnace
Propane stove with oven
Lots of 12v lighting fixtures, wiring, receptacles, switches, etc.
Battery (may not be have that much good life left in it, however)
Converter, Inverter, Control/distribution panel, gauges

Naturally, these will vary by unit.

FWIW, I gutted and rebuilt the interior of a 5th wheel rig, using many salvaged parts.

In closing, once you strip the trailer of all thats good for re-use, the trailer can become a storage shed, workshop, or whatever secondary use you have for it. Or, you can sell the remainer to a scrap dealer, especially if it's and older one clad with aluminum.

Lee

__________________
Reply With Quote
  #6  
Old 11/10/09, 08:31 AM
 
Join Date: Feb 2005
Location: Mid-Michigan
Posts: 1,526

Since you already have a power system in place, I think a better approach would be to get a more efficient fridge and/or upgrade the power system. The propane will be an added expense and unless you are already using it for heating, it'll be an extra task to worry about filling & moinitoring the tank. There are some articles on line about building a very efficient fridge from a chese freezer, you might look into that.

__________________

Check out my Blog to see what's happening on the homestead!
Automatic Chicken Coop Door Plans

Reply With Quote
  #7  
Old 11/10/09, 09:17 AM
7thswan's Avatar
 
Join Date: Nov 2008
Location: michigan
Posts: 18,298
Quote:
Originally Posted by cfabe View Post
Since you already have a power system in place, I think a better approach would be to get a more efficient fridge and/or upgrade the power system. The propane will be an added expense and unless you are already using it for heating, it'll be an extra task to worry about filling & moinitoring the tank. There are some articles on line about building a very efficient fridge from a chese freezer, you might look into that.
That's true, We just got a new Fridge, there was a tag on it that said it would only cost $43 dollars for the whole year and it has an ice maker.
__________________
Reply With Quote
  #8  
Old 11/10/09, 11:15 AM
 
Join Date: Nov 2002
Location: Alaska
Posts: 4,527

This house was already set up off-grid so we're still tweaking the system, learning the nuances and figuring out what needs to be replaced. It runs off a spring (pelton wheel) so we're also up against winter for some of the changes we can make. We'll probably end up reworking the spring head and some of the piping next year to try to get longer use out of the system (currently freezes up part of the year). I KNOW DH hadn't considered the cost of propane. He's got TV on the brain right now

__________________
http://maysmissive.blogspot.com/
Reply With Quote
  #9  
Old 11/10/09, 02:39 PM
texican's Avatar  
Join Date: Oct 2003
Location: Carthage, Texas
Posts: 12,052

Back when I was off grid, the propane fridge was the only way to go... I had/have free natural gas. The only negative is that it's a booger to keep things cold or frozen, especially if it's hot outside. I could have ice or ice cream, but not both.

My fridge, a Sibir, died about year 12, when one of the return tubes rusted through! Why, I don't know.... it's still in the barn, in case I someday figure out how to cut out the bad spot, splice it with new tubing, and recharge the puppy with ammonia.

What I want is an icy/ball... will have to make one one of these days...

__________________

Luck is what happens when preparation meets opportunity. Seneca
Learning is not compulsory... neither is survival. W. Edwards Deming

Reply With Quote
  #10  
Old 12/07/09, 05:42 PM
Registered User
 
Join Date: Dec 2009
Posts: 15
Efficiency

Hi folks!

I've been doing some homework on the fuel consumption of the various forms of kitchen refrigerators, and, if I did my math right, found out some interesting things.

It's not too hard to compare the gas operated ones, as you can convert the gallons used in the LP models to the Dekatherm's Oklahoma Natural Gas (the supplier where we live) uses to calculate the cost of natural gas. The electrically-operated figures may or may not be correct - there is a LOT of differing opinions as to the average killowatt hours the typical machines use, but the following gives a good idea.

The modern LP-operated gas refrigerators are rated at 1.1 gallons of propane use per day. The older Servel's use 2.5 gallons per day.

At the current cost of propane here in NE Okla, that means:

* Cost of running the newer (1.1 gal/day of LP) units = $0.45/day, $13.30/mo, $159.60/yr
* Cost of running the Servel's (2.5 gal/day of LP) units = $1.13/day, $33.90/mo, $406.80/yr

Now - using the formulae found at http://www.energykinetics.com/saving...parisons.shtml, I converted the amount of LP gas used by both types of refrigerators to comparable amounts of natural gas, and came up with this:

*Cost of running the newer (1.1 gal/day of LP models on NG) units = $0.15/day, $4.50/mo, $54.00/yr
* Cost of running the Servel's (2.5 gal/day of LP models on NG) units = $0.375/day, $11.25/mo, $135.00/yr

However - this assumes that the amount of gas use is the same, and I'm not totally convinced that it is, as LP gas is much hotter than natural gas (more BTU output). Therefore, I have asked the people at Crystal Cold to tell me what the NG consumption of their refrigerators actually is. If it's different than why I've calculated above, I'll let you know.

As for electric refrigerators, the numbers are all over the board - each manufacturer and each website claiming to know what they're talking about gives a different rate of electricity usage for the various types/ages of refrigerators out there. That said, I believe the following is close to being accurate:

* Cost of running an electric refrigerator (avg efficiency) = $0.63/day, $19.12/mo, $229.44/yr
* Cost of running an electric refrigerator (high efficiency) = $0.23/day, $6.75/mo, $80.96/yr

SO - it would appear that the most fuel efficient refrigerator is a modern absorption-type using natural gas, and it costs the least to operate, followed by the high-efficiency electric model, followed by the lowly vintage Servel on natural gas, followed by the modern gas unit using LP, followed by by the older, less efficient electric unit, and, bringing in the rear, is the older Servel on propane.

Note: Pricing based on the cost of fuel here in Oklahoma. All units based on the same BTU output needed to provide the same amount of cooling.

Hope this helps someone!
http://vintageservelrefrigerators.8k.com

Todd W. White

__________________
Reply With Quote
  #11  
Old 12/07/09, 08:38 PM
 
Join Date: May 2006
Location: north central wv
Posts: 2,314

Just don't hook a propane unit up to nat gas, nor a nat gas unit up to propane. They have different size orfices [SP} in them. Or any unit out of a rv as most are set up for propane. Good luck getting what you want. Sam

__________________
Reply With Quote
  #12  
Old 12/07/09, 08:49 PM
Registered User
 
Join Date: Dec 2009
Posts: 15
Orifice's

That's right -

You have to make sure the unit you have is setup for the type of gas you are using. This is why it's so important that you get the service manual for it, which are usually available, even for the old Servel's.

When I rebuilt mine, I ordered a new orifice and turbulator for the specific cooling unit (2600 BTU's) and the type of gas I use (natural), as it was originally setup for LP gas.

__________________
Reply With Quote
  #13  
Old 12/07/09, 09:26 PM
ca2devri's Avatar  
Join Date: Feb 2008
Location: Southwestern Ontario
Posts: 207

I don't mean to nit-pick, Todd - but I think you mean that the natural gas is the cheapest, not necessarily the most efficient. The fact that it costs less may just reflect the fact that electricity is more $$ per kWhr / BTU of power.

Chris

__________________

Chris DeVries
Common Ground CSA
http://csa.amandadevries.com

Reply With Quote
  #14  
Old 12/07/09, 11:01 PM
 
Join Date: Nov 2002
Location: Alaska
Posts: 4,527

Great research and information, Todd!

We've decided to go with something a little less conventional than any of the above options. The worst part about a refrigerator is that the door opens to the front, letting the cold air out every time you open that door. After a ton of research on as many of the options as we could find, we decided to use an energy efficient chest freezer with an external thermostat like this one:

http://www.midwestsupplies.com/produ...px?ProdID=4230

Chest type freezers are much more efficient than the most efficient uprights AND they cost less to purchase as well. The freezer we purchased has quite a few baskets and I'll probably use some milk crates in the bottom of the freezer to make it easier to get stuff out. We'll work up an easier way to retrieve stuff once we have the freezer here and play with it a bit. I suspect the biggest adjustment will be mental

__________________
http://maysmissive.blogspot.com/
Reply With Quote
  #15  
Old 12/07/09, 11:24 PM
 
Join Date: Apr 2005
Location: Minnesota
Posts: 259
Quote:
Originally Posted by Todd W. White View Post
The modern LP-operated gas refrigerators are rated at 1.1 gallons of propane use per day. The older Servel's use 2.5 gallons per day.
I think you mean pounds not gallons.

The current national average for propane is $2.28 per gallon or $0.785 per pound. The average yearly cost to run a modern servel is then $222.73. ($2.28/4.11 X 1.1 X 365)

You must also consider that these refrigerators are only 8 cubic feet.

Quote:
* Cost of running an electric refrigerator (avg efficiency) = $0.63/day, $19.12/mo, $229.44/yr
* Cost of running an electric refrigerator (high efficiency) = $0.23/day, $6.75/mo, $80.96/yr
These are for large refrigerators 18+ cu. feet and you are thus comparing apples to oranges.

Let's look at a brand new GE Spacemaker® Compact Refrigerator Model #: GMR06AAPBB which, at 5.7 cubic feet, is a better comparison. It will use 360 KWh per year; the US average rate is $0.1205 per KWh; which means the total yearly cost is $43.38 to operate.

So then, using a modern servel is 5 times more expensive than using a comparable electric fridge.

whistler
__________________

Last edited by whistler; 12/07/09 at 11:47 PM.
Reply With Quote
  #16  
Old 12/07/09, 11:45 PM
 
Join Date: Apr 2005
Location: Minnesota
Posts: 259
Quote:
Originally Posted by Todd W. White View Post
Now - using the formulae found at http://www.energykinetics.com/saving...parisons.shtml, I converted the amount of LP gas used by both types of refrigerators to comparable amounts of natural gas, and came up with this:

*Cost of running the newer (1.1 gal/day of LP models on NG) units = $0.15/day, $4.50/mo, $54.00/yr
* Cost of running the Servel's (2.5 gal/day of LP models on NG) units = $0.375/day, $11.25/mo, $135.00/yr

However - this assumes that the amount of gas use is the same, and I'm not totally convinced that it is, as LP gas is much hotter than natural gas (more BTU output).
If we want to compare natural gas we have to take an extra step - compare BTU to BTU. A pound of propane has approximately 22,154 BTUs. Currently, 22,154 BTUs of natural gas costs $0.313. (The current national average for natural gas is $0.0000141477 per BTU) Thus it would cost $125.84 to run the newer Servel on natural gas per year. ($0.313 X 1.1 X 365)

Again electricity comes out the winner; this time by a factor of almost 3.

Whistler
__________________

Last edited by whistler; 12/07/09 at 11:50 PM.
Reply With Quote
  #17  
Old 12/08/09, 10:56 AM
Registered User
 
Join Date: Dec 2009
Posts: 15
Corrections

Well, let me see if I can make a little more sense....I went back and revisited this issue, using the BTU's required to operate, as suggested above, and I "think" the following is correct. I was a victim of the "New Math" program in the US public school system of the 1960's, where the emphasis was on teaching me "why" I was doing the math, rather than how to get the correct answer, so here goes -

Crystal Cold rates their smallest (12 cubic foot) and largest (18 cubic foot) refrigerators use use .35 gallons per day. The BTU usage of the small one per day is 1750/hr, and the large one is 1825/hr.

So - we have the amount of BTU's these things consume per hour.

Now - there are 95,500 BTU's in a gallon propane.

So -

The 12cf unit uses 1750 BTU's/hour. 95,500/1750 = 54.57 hours from one gallon of LPG, which = 2.27 days (54.57/24).

The 18cf unit uses 1825 BTU's/hour. 95,500/1825 = 52.33 hours from one gallon of LPG, which = 2.18 days. In other words, they're essentially the same.

That means it takes 13.21 gallons of LPG to operate the 12cf unit for 30 days (30/2.27), and 13.76 gallons of LPG to operate the 18cf unit for 30 days (30/2.18).

At the current rate of $1.89/gallon of LPG here in Oklahoma, that breaks down as follows:

The 12cf unit will cost $0.83 per day (13.21 x 1.89, divided by 30) to operate, and the larger, 18 cf unit will cost $0.87 per day (13.76 x 1.89, divided by 30) to run.


Now - let's translate that into use of natural gas.

Natural gas has 1,000,001 BTU's in a DekaTherm, which is the unit Oklahoma Natural Gas, where I live, prices their gas.

The 12 cf unit requires 1750 BTU/hour to operate, and the 18cf unit uses 1825 BTU/hour.

1,000,001/1750 = 571.43, so that means we get 571.43 hours of use out of our 12cf unit out of each DekaTherm, which = 23.8 days (571.43/24). The cost here of 1 DekaTherm of natural gas is $6.75.

1,000,001/1825 = 547.95, so that means we get 547.95 hours of use out of our 18cf unit out of each DekaTherm, which = 22.8 days (547.95/24). The cost here of 1 DekaTherm of natural gas is $6.75.

So -

The 12 cf unit will cost $0.28 per day to operate on natural gas ($6.75/23.8), and the larger 18 cf unit will cost $0.30 per day to run (1,000,001/1825 = 547.95, and 547.95/24 = 22.83 days, and $6.75/22.83).

In other words, if I got this right this time -

To produce the same amount of BTU's -

* The 12 cf unit costs $0.83 per day to operate on LP gas.
* The 18 cf unit costs $0.87 per day to operate on LP gas.

* The 12 cf unit costs $0.28 per day to operate on natural gas.
* The 18 cf unit costs $0.30 per day to operate on natural gas.


With regard to the older Servel's, let use my 1955 Model 856G as an example.

My Servel is around 12 cubic feet inside, and has a cooling unit rated at 2600 BTU's, so let's plug in that number into our equation, and the results are:

My Servel uses 2600 BTU's/hour. 95,500/2600 = 36.73 hours of operation from one gallon of LPG, which = 1.53 days of use per gallon. 30 days divided by 1.53 = 19.6, so it uses 19.6 gallons of propane per month.

That means it takes $37.04 to operate my Servel for 30 days on LPG (19.6 gallons x $1.89 per gallon).

This translates to an actual operating cost of $1.23 per day ($37.04 divided by 30).

With respect to natural gas -

My Servel requires 2600 BTU/hour to operate. There are 1,000,001 BTU's in a DekaTherm of natural gas.

1,000,001/2600 = 384.62, so that means I get 384.62 hours of use out of my Servel out of each DekaTherm, which = 16.03 days (384.62/24). At the current cost here of 1 DekaTherm of natural gas of $6.75, that means my Servel costs $0.42 per day to operate on natural gas ($6.75/16.03)

That should be comparing apples, er, BTU's to BTU's.


Now, let's look at a similarly sized electric model.

General Electric's GTR12HBXRWW is a 12 cubic foot electric refrigerator. It requires 412 kwh per year to operate, which equals 1.13 kwh per day to run.

General Electric's GTS18IBRBB is an 18 cubic foot electric refrigerator. It requires 478 kwh per year to operate, which equals 1.30 kwh per day to function.

The current price per killowatt hour where I live is, averaged for the year, is $0.034 er kwh.

Bottom Line:

* The 12 cf unit costs $0.83 per day to operate on LP gas, and $0.28 per day on natural gas.
* The 18 cf unit costs $0.87 per day to operate on LP gas, and $0.30 per day to operate on natural gas.
* The older Servel, like mine, costs $2.89 per day to operate on LP gas, and $0.42 per day on natural gas.
* GE's 12 cf electric unit costs $0.04 per day to operate (1.13 x $0.034), and
* GE's 18 cf electric unit costs $0.044 per day (1.30 x $0.034) to run.


So, yes, Whistler is right about the electric being less costly to operate, though I wonder what the price to operate them, amortized over time, would be, with respect to longevity and the cost of parts and service...I suppose we'll never know that.

Of course, this is supposing a person has access to the electrical grid - if you don't, you can plug the cost of whichever type of gas is available to you to determine the cost of operating a gas refrigerator, as the cost of running a generator to run an electric one would be, in my estimation, way too much.

If I made any errors in all this, I am certainly open to correction.

- Todd

__________________

Last edited by Todd W. White; 12/08/09 at 11:50 AM. Reason: ...fixed a typo.
Reply With Quote
  #18  
Old 12/08/09, 11:44 AM
 
Join Date: Nov 2002
Location: Alaska
Posts: 4,527
Quote:
Originally Posted by Todd W. White View Post
Of course, this is supposing a person has access to the electrical grid - if you don't, you can plug the cost of whichever type of gas is available to you to determine the cost of operating a gas refrigerator, as the cost of running a generator to run an electric one would be, in my estimation, way too much.

If I made any errors in all this, I am certainly open to correction.

- Todd
Most off-grid people have some form of elec, usually solar, wind or water (less common) so their cost comes primarily from setting up and maintaining the system. A gas or diesel generator is usually not the main source, might be backup. Very hard to set a cost because you don't always know how long the parts will last when you set it up. Our system was already in place. We're tweaking to try to get more out of it. Going to look at LED lights today to replace HUGE fluorescent units which suck a pile of energy when you have such big ones.
__________________
http://maysmissive.blogspot.com/
Reply With Quote
  #19  
Old 12/08/09, 11:53 AM
Registered User
 
Join Date: Dec 2009
Posts: 15

Servel (the real one - not the folks at Dometic) made an electric version of their gas-fired absorption refrigerator. As best I can tell, the only difference was it had an electric heating element providing the heat, rather than the gas flame.

Since these systems have to have continual heat to operate, even though it fluxuates depending on the amount of cold needed, the element in an electrically-operated system would have to be "on" all the time, and the element would have to be turned hotter and cooler, as needed.

With the advances in technology, I'm wondering if it would be possible to put a high-tech element in there to do the job the flame does, and make it more close in efficiency (and, therefore, operating costs) as the compressor-type electric fridge...

__________________
Reply With Quote
  #20  
Old 12/08/09, 08:49 PM
Registered User
 
Join Date: Dec 2009
Posts: 15
Caveat...

I've put in calls and email's to the Gas Co. and the folks who make/sell the different modern gas refrigerators.

What I am trying to determine is:

A. What the gas consumption of the refrigerators is when setup for natural gas (not asking the Gas Co. this).

B. Does an appliance setup for propane use the same amount of gas when switched over to NG.

The answers I get may change my report...

They DID! See below -

__________________

Last edited by Todd W. White; 12/09/09 at 04:53 PM. Reason: Updated information
Reply With Quote
  #21  
Old 12/08/09, 09:12 PM
 
Join Date: Jul 2009
Location: Pa
Posts: 508

I noticed when comparing cost of gas vs electric everyone is using the avg cost of grid electricity but the question was based on off grid use so the comparison has to be between the cost of gas vs solar installation. As far as propane vs natural gas you need to be on a gas grid to get natural gas unless you have a gas well. We stayed far from the topic of Off grid refrigeration.

__________________
Reply With Quote
  #22  
Old 12/09/09, 08:08 AM
 
Join Date: Jan 2004
Location: PA
Posts: 5,291
Quote:
Originally Posted by NCLee View Post
RV, travel trailer salvage yards are good places to find the dual fuel (110V/propane) refrigerators at a good price. Mine came from a travel trailer that had been wrecked.

Also, consider buying a used travel trailer to strip it of all the components that are useful in living off the grid. This time of year, people are more likely to get rid of them because they don't want to spend money to store them over the winter. The cost of the whole unit can be much less than buying the applicable components separately.

Dual fuel refrigerator
12v water pump
Propane furnace
Propane stove with oven
Lots of 12v lighting fixtures, wiring, receptacles, switches, etc.
Battery (may not be have that much good life left in it, however)
Converter, Inverter, Control/distribution panel, gauges

Naturally, these will vary by unit.

FWIW, I gutted and rebuilt the interior of a 5th wheel rig, using many salvaged parts.

In closing, once you strip the trailer of all thats good for re-use, the trailer can become a storage shed, workshop, or whatever secondary use you have for it. Or, you can sell the remainer to a scrap dealer, especially if it's and older one clad with aluminum.

Lee
That's a darn good idea..

Now to look for a RV scrap yard...
__________________

Pennsylvania Constitution, Article 1 Section 21 "The Right of the Citizens to bear arms in defense of themselves and the State shall not be questioned"
www.pafoa.org
http://www.45thpacok.com

Reply With Quote
  #23  
Old 12/09/09, 01:47 PM
 
Join Date: Aug 2006
Posts: 58

Here is an idea for cold climates...not made yet, but DIY would be possible...

http://winref.com/

Kev

__________________
Reply With Quote
  #24  
Old 12/09/09, 02:14 PM
aka avdpas77
 
Join Date: Dec 2008
Location: central Missouri
Posts: 3,211

I don't remember the brand, but my grandfather had a double door LP fridge (no freezer)that worked terrificly and ran for at least 25 years with no problem. It did have a little fan underneath that ran off of electricity, it was not required, but made the thing more efficient. I am not sure when it was purchased, I am thinking some time between the 20's and the 50's, because it was the only gas refridgerator I ever saw when I was young and was already humming away when I was born. I wish I knew what happened to it whe he passed away. His kitchen stove and his fridge both ran off a 100lb tank, and it didn't have to be chainged very often.

__________________
Reply With Quote
  #25  
Old 12/09/09, 04:52 PM
 
Join Date: Dec 2009
Location: Montana
Posts: 436
Quote:
Originally Posted by Todd W. White View Post
I've put in calls and email's to the Gas Co. and the folks who make/sell the different modern gas refrigerators.

What I am trying to determine is:

A. What the gas consumption of the refrigerators is when setup for natural gas (not asking the Gas Co. this).

B. Does an appliance setup for propane use the same amount of gas when switched over to NG.

The answers I get may change my report...
Answer to A:You will never get an answer. Manufactures have standardized with the "do not convert to any fuel not listed on the rating plate" since the late 90's for liability reasons. The old answer was yes, you are after a heat value to do the task not a concern of what you burn for that amount of heat.
Answer to B:When properly done so yes.
__________________
Reply With Quote
  #26  
Old 12/09/09, 05:02 PM
Registered User
 
Join Date: Dec 2009
Posts: 15
Updated Info On Energy Use...

Hello all!

Well, after a LOT of difficulty, I finally got some definitive answers from the local natural gas company, the people at Crystal Cold, the electric company, and the local propane people. The propane people were very nice, the natural gas people were when I finally got to the right person, and the electric company had to be asked repeatedly before I got them to tell me the truth.

What follows is a summation of that information. 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 they are 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 (you were correct about my error in my earlier post - these numbers are correct).

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, so the old one, though it looks "neat", uses more than twice the amount of energy than a new one.

Now - 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. If you average it out, the cost is $0.53 per kwh (13 divided by 30 = $0.43 + $0.084/kwh).

That means -

General Electric's GTR12HBXRWW 12 cubic foot electric refrigerator, which they say requires 412 kwh per year to operate, uses 1.13 kwh per day to run, which equals $0.60 per day to operate (1.13 x $0.60).

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 function, which equals $0.69 per day to operate (1.13 x $0.60).

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

Now that we have the correct numbers, if I did the math right, 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 $0.60 per day to operate, and
* GE's 18 cf electric unit costs $0.69 per day to run.


That means that what some of us suspected is actually true - that the modern gas-fired refrigerators are quite efficient, and their electric counterparts are, indeed, not as cheap to run as we might have been led to believe...

I truly hope that 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.

Again, if I made any errors in computation, do let me know...

- Todd

__________________
Reply With Quote
  #27  
Old 12/10/09, 10:46 AM
 
Join Date: Apr 2005
Location: Minnesota
Posts: 259

All was looking good until you got to this point.

Quote:
Originally Posted by Todd W. White View Post
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. If you average it out, the cost is $0.53 per kwh (13 divided by 30 = $0.43 + $0.084/kwh).
No, this is plain wrong. Each KWh costs $0.084 plus X, which can be defined as a proportion of the base cost. X is determined by dividing $13 (the monthly service charge) by the total monthly KWh.

In your original formulation, if you use 1000 kWh per month your electric bill would be $530. Most of us would about die if that were the case. Instead your electrical bill should be equal to $0.084 * 1000 + $13, or $21.40.

Thinking quickly you realize that as you use electricly less the relative cost of each KWh increases.

Therefore:

Quote:
That means -

General Electric's GTR12HBXRWW 12 cubic foot electric refrigerator, which they say requires 412 kwh per year to operate, uses 1.13 kwh per day to run, which equals $0.60 per day to operate (1.13 x $0.60).

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 function, which equals $0.69 per day to operate (1.13 x $0.60).

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

Now that we have the correct numbers, if I did the math right, here's the -

Bottom Line:

.....


* GE's 12 cf electric unit costs $0.60 per day to operate, and
* GE's 18 cf electric unit costs $0.69 per day to run.


That means that what some of us suspected is actually true - that the modern gas-fired refrigerators are quite efficient, and their electric counterparts are, indeed, not as cheap to run as we might have been led to believe...
Is wrong.

--------

Let's assume that your refrigerator is the only electrical appliance in your house:

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
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.


This isn't too far off your fomulation.

-----------


Let's assume, now, that you have the full complement of electrical appliances in your house and use 1000 kWh per month (the US average):

The new formula for the 12 cu. ft. fridge is: 1.13 X $0.084 + $13/1000. Thus it costs $0.107 per day to run.
Using a the same formula with the 1.3 instead of 1.13, the 18 cu. ft. fridge costs $0.122 per day to run.

This is a dramatic difference from your formulation.


--------

Whistler
__________________

Last edited by whistler; 12/10/09 at 10:49 AM.
Reply With Quote
  #28  
Old 12/10/09, 11:11 AM
 
Join Date: Nov 2002
Location: Alaska
Posts: 4,527
Quote:
Originally Posted by kbabin View Post
Here is an idea for cold climates...not made yet, but DIY would be possible...

http://winref.com/

Kev
Easier yet is to just put the freezer out on the porch. That's how we're managing the chest freezer used as a freezer part right now. Not as handy as that picture, but it works pretty well and only runs a little bit every day! The freezer as fridge will go in the room off the kitchen that stays relatively cool. That freezer arrived yesterday so I'm just waiting for the analog plug in device. Lowes had no LED kitchen lights other than under cabinet lighting but I found some online.
__________________
http://maysmissive.blogspot.com/
Reply With Quote
  #29  
Old 12/10/09, 11:24 AM
Registered User
 
Join Date: Dec 2009
Posts: 15
Cost of Electricity

Hi Whistler,

I appreciate your help on this - I'm not trying to be "The Expert" here, just trying to help. Sorry about the calculation error.

You are correct when you calculated it as -

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

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.


Sorry about that!

However - I didn't include the other items, because I was trying to make as close to an apples-to-apples comparison as possible, something NONE of the utility companies seem to want me to do.

THANKS for the clarification!

- Todd

__________________
Reply With Quote
  #30  
Old 12/10/09, 11:28 AM
 
Join Date: Dec 2009
Location: Montana
Posts: 436

My old freezer has a heating strip for the motor and compressor that comes on if the room temp drops below freezing. I would check that out.

Todd, If your old Servell ever quits working one fix was to turn it upside down, empty it of course, and leave it for a couple of days. That helped get the cooling solution back into sync.

__________________
Reply With Quote
Reply



Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -5. The time now is 12:22 AM.