Propane refrigerator

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.

That's a darn good idea..

Now to look for a RV scrap yard...

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

http://winref.com/

Kev

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.

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.

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

All was looking good until you got to this point.

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:

Is wrong.

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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.

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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.


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Whistler

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.

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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

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.

Hello Gianni!

Yes, that is the prescribed method - what happens is that people often don't set them level, and, since it is a gravity-fed flow, some of the chemicals settle out and solidify, and eventually stop them up. Turning one upside down breaks these pieces (which are quite small anyway) up and the fluids can flow again. Ultimately, though, it will need to be depressurized, evacuated, flushed, and recharged, as, if allowed to operate for too long like that, the fluids become verrry caustic and begin to eat the pipes from the inside out.

I'm not trying to be the expert either :baby04: Getting all of ones ducks in a row is often a bit complicated with alternative energy numbers. It's always nice to have a couple of people take a look at the problem.

Whistler

Sure is!

It is very difficult to get all of these energy sources "on the same page", as they almost seem to purposely veil the actual cost of their products from the consumer so that we can't figure out what really costs what. Even the "expert" websites disagree on the conversions/comparisons, which made coming up with these numbers all the more difficult. Further, not everyone agrees on how many BTU's are in a particular unit of measure, so I had to go with what appeared to be the ones that were most commonly adhered to.

Again - THANKS for all you help! After a while, all those numbers can give one a headache...

We've been running our new "chest refrigerator" for a few days now and LOOOOOVE it!!! It runs about 10 min per hour (or less) as opposed to our old one which easily ran 30 min per hour. It has made a huge difference in our energy consumption! Basically, when it runs, it runs for about 10 min. That's usually less than once per hour but about once per hour if we've been in and out of it. Lowest temp is at the bottom after it runs, about 35 degrees. Highest temp at the top before it runs, about 40 degrees. Not bad! It's got so many baskets that stuff is easy to get. Stuff I don't use often (extra milk and peanut butter, etc) goes way down under the baskets.

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The idea of a gas-powered chest freezer interests me - I may start looking for one!

Thanks for the positive report on them!

??? Ours isn't gas powered. Were you referring to another post? Ours is electric, but we are using the chest freezer as a refrigerator.

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Natural gas is the cheapest and most efficient, if your gas is free. If you live in an established gas producing area, you might qualify for free gas rights. I've got the gas heaters on overdrive here... and I don't worry... as I have unlimited free gas rights...

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Hi longshadowfarms -

Sorry, I misunderstood - I thought you were speaking of yours as though it were gas.

Texican - interesting idea. Tell me more...

Yea don't rely on propane..

In Aug we had to pay about $2.29 per Gal.
In Dec it was $4.50 per gal delivered in both instances... Glad we only use it to cook and for hot water...

I almost called them and told them to shove their gas... but I need it for now for hot water...

Now if you are lucky enough to have gas rights from your porperty, then it might be worth it...

I may even get a electric water heater, even if it is just to tell the gas company that I got one and that they better re-think their pricing...

I do have one sitting around already, even though it isn't any good.. It was given to me for scrap...

__________________
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

DH has me keeping an eye out for a good used propane RV refrigerator. Doesn't have to be big. Also going propane route for an on demand hot water heater. Have had them in the past and really like them. We lowered our LP use 80 gallons in one year by switching to one.

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