refrigeration for off grid homes

[MountainDon]

The SunFrosts are expensive! I found the RF-16, (14.3 actual cu ft, fridge/freezer total, pretty much the minimum size I'd want) for $2498 in DC - $2630 in AC.   http://www.affordable-solar.com/DC.Refrigerator.Freezers.htm   It has an Energy Star rating of 254 KwHr per year.

I did some checking into efficiency ratings (Energy Star) of refrigerators.  http://www.energystar.gov/

When you can buy a refrigerator, such as a Fridgidaire 14.8 cu. ft. top freezer model FRT15HB3DZ from Lowe's for $448 with a rated use of 376 KwHr per year it gives one cause for a second look at the numbers.
Sunfrost      14.3 cu.ft.      $2500            254 KwHr per year = .7 KwHr per day  
Fridgidaire      14.8 cu.ft.      $450            376 KwHr per year = 1.03 KwHr per day
The Sunfrost uses apprx 33% less energy than the Fridgidaire, but costs 555% more to purchase.

Using JamesTheLess's figure of 50 cents/KwHr for off grid power (which is a little high, see note ***below)
Sunfrost operating cost = $127 per year
Fridgidaire operating cost = $188 per year, only $61 a year more.
Hmmm.. $2000 purchase cost savings divided by $61 = 32.7  years to break even point.

Anybody see any holes in my reasoning?

OK, the figures may be a little off because the cost of an inverter to run the Fridgidaire is not included, and the Sunfrost model I choose runs directly off 12 or 24 VDC to save on inverter losses. But I'm going to have an inverter anyways. Maybe I might need a little bigger one, maybe not. I'll have to re-run my projected uses.

I think I just talked myself out of ever buying a Sunfrost.

***NOTE: link gives computed cost for solar electricity price index, updated monthly.
http://www.solarbuzz.com/SolarIndices.htm

Final note; To my way of thinking,the choice between the Sunfrost and the Fridgidaire would be like being given a choice between a Honda Civic (my car, a 2006) that gets 32 MPG in my real life use for $18K or the same car giving 47 MPG for $90K.

Thoughts?

[Amanda_931]

Boats have even more exotic refrigeration systems available.

With a very very pricy compressor (this makes the sun-frosts look cheap!) and access to water one can, if I read it right have one little six-pack sized compressor that can refrigerate, and freeze ice cubes and fish and cool a room.

Exotic insulation available from them, too.

http://www.glacierbay.com/marine_index.asp

Seems like some company had a refrigerator built something like this for less than the sun-frost.  I couldn't find it the other day when I was looking.

If you are 12 (or 24) volt only, then the sun-frost makes better sense.

The travel trailer refrigerator runs on 120 v or propane.  I haven't noticed a long time for it to cool down.  (some are triple-power--adding 12v to the mix).  But then I moved into it in the winter time.

[MountainDon]

The travel trailer refrigerator runs on 120 v or propane.  (some are triple-power--adding 12v to the mix).

The 12 VDC option on RV fridges is really only meant for use while on the road as it's a resistance heater, and will suck your battery dry in a hurry when stopped.

[Amanda_931]

You're right!

(but does it cool faster with electricity than propane?)

[glenn-k]

I have had really bad luck trying to get my RV fridge to work at all on electricity so in my opinion it doesn't work as good.  Only tried it once or twice and wasn't happy with the attempt.

[MountainDon]

(but does it cool faster with electricity than propane?)

It depends! I know you didn't want to hear that..

IF the voltage is right up where it should be, and IF the propane burner is correctly adjusted and you are below 1000 ft elevation, there should be not a noticeable difference.

My own RV fridge cools off quicker on AC power using a 10/3 - 25 ft cable. than it does on propane. I think that is because of the altitude; about 5400 ft on the home driveway and nearly always higher in our favorite travel places. With the decrease in air pressure and oxygen as you go up the flame doesn't burn as hot. The RV refrigeration manuals I've read always strongly suggest testing a units performance on AC power rather than propane because of this.

Sorta like a naturally aspirated gas or diesel engine looses power. A rough rule of thumb is 3% loss for every 1000 ft of altitude. That's especially important as well when talking generators. At an 8000 ft altitude a 4000 watt gen is only good for about 3000 watts.

[glenn-k]

Good point, Don.  Sometimes I forget how high I am. :-?

[MountainDon]

I have had really bad luck trying to get my RV fridge to work at all on electricity so in my opinion it doesn't work as good.  Only tried it once or twice and wasn't happy with the attempt.

Could be the heater element has a problem.

[glenn kangiser]

Could be possible - I never checked it - just got more propane.

[Erin]

My folks have had a gas refrigerator in their "off-grid" cabin for 25 years (a Servel from the 40s, I would guess).  It's always worked quite well.  
There is a bit of a "warm-up" period, but usually within a few hours, it's going well enough to keep icecream frozen in the freezer.
They also have another out in a privvy-type building for nothing but beverages on holiday weekends.  8-)

And due to the increasing rarity of fridges of this vintage, Dad also has 3 more out in their garage in various states of quality.  (Is it odd to collect gas refrigerators?    :-? )  
He snags his at auctions, though there are fewer and fewer of them available.  (The price of new ones...Oh my!!)

[Amanda_931]

I've usually run mine on 120 v., don't notice a problem (dometic--now allied with Servel)

[glenn kangiser]

I found one at the dump and snagged it for spare parts -- I'm not a real dump scavenger but can't pass up a good deal once in a while - we needed the water condensate tray - and got it.

[bnix]

at

http://www.gotoreviews.com/