Off Grid Appliances: Propane vs Electric

[AdironDoc]

As the planning of my off-grid system shapes up, I'm beginning to look at appliances and their power requirements. With a total of just 8000W of battery, one wind turbine and one planned solar panel at around 200W, I'd like to keep to the essentials. Seems the lion's share of power typically goes to refrigeration (1Kw/day) and the cost of a SunFrost ref is over $2K. 

The propane models are like the girl I never noticed and then one day... Well, given the circumstances, the LP units suddenly seem very attractive. The 12cu/ft combo uses a quarter gallon/day and can run on 120V too. A dedicated 40#  (9.4gallons) tank should last 36 days. Not bad considering I'd only been at camp some weekends.

With off-grid electricity being a precious thing, are most of you using propane appliances? Refrigerators, AC, etc? Any advantages to staying electric and running them off an inverter? Any good reason to run all appliances off one big tank or can I go easy on my back and lug a separate tank for each?

Cheers,
Doc

[Squirl]

There are a few ways people have over come this.
1. Some can get a chest refrigerator.  They use less electricity.
2. Some people add more insulation around a standard refrigerator.
3. Some people go old school and go with an ice chest.  In your area the average low temperate is below freezing for 6 months out of the year.  And the average night time temperature is around the temperature of a refrigerator for a few more months. 
4. In today's market some people are just sizing up their off grid system. Smaller energy star refrigerators are rated for 1kw a day.  I read an article about the testing between a $400 energy star refrigerator and a $2000 + shipping sunfrost version was only .1-.2 kwh a day.  With cheap panels at $2.50 a watt, it can be cost effective to simply upsize.  Personally, I would like the price security because petroleum products can vary a lot in price over time.  Also, I wouldn't have to haul as much propane.
Also, be careful about your refrigeration setup.  The heat coils against a wall, next to a stove, and without air circulation can have a very large impact on efficiency, no matter what you buy.

On a side note, I have noticed that many of your posts are on off-grid electricity and energy.  I myself share a passion on this subject.  Once, I received an online subscription to homepower magazine.  I would recommend it because you can access many great articles for 3 years prior and the next two years.  Also I believe they sell all their articles on CD for pretty cheap. 

[MountainDon]

Tanks: By big tank do you mean a 200+ gallon on the ground, refilled by a truck? Or 100 pound vs 30, 30 pound?

I'd like a 200+ plus we don't use enough to be able to get a cheap rental and they are too much to buy. I put in an RV regulator with auto changeover. I like that as with using a couple of 40 pound cylinders we never run out. The regulator switches from one to the other tank without missing a heartbeat. I like that better than a tank for this and that. But that is me. I have three 40 pounders and a couple 20's because I am paranoid about running out in the winter. Even though last winter we did not even use two 40's.  


Refrigerator: We went propane with a Servel RGE400 (from thenaturalhome.com, nice people and the best deal I found a couple years ago). They also offer an exterior vent kit which I bought. They do not sell it separately and I've not seen it elsewhere. It supplies freesh air to the burner and takes the burner exhaust outside. No CO danger and propane fridges are bad for that IF the burner is not cleaned at least yearly. They are especially bad if left sitting turned off, like over winter. Spiders love the burner and chimney for some reason. With some web in there the air flow can be restricted and that = CO. Our neighbors had a real bad case of CO poisoning a couple years ago. From their fridge. But with the burner clean we've never registered any CO (fresh air kit goes in come spring.... a little slow....)

If you look at the burner specs for the different brands of propane fridges you will see that they all are rated at 1500 to 1700 BTU/HR, no matter the size of the refrigerator itself. Our Servel is called an 8 cu ft (actual measurement is 7.3 cu ft (5.9 + 1.4 freezer. I think that is a common thing with fridges).  The burner used in the Crystal Cold, for example, is rated at 1700 BTU/HR, but their boxes are 12, 15 or 18 cu. ft. (Crystal Cold boixes are Frigidaire and the Amish add the burner, etc.) So it seems to me that if the box construction is more or less the same, more or less the same level of insulation, the burners very close in size, then the larger boxes may have more trouble keeping a good cold in hot weather. Also they would be slower to cool down.  

The consumption specs are usually given for 75 degrees F ambient, so real world could be better or worse.

I read someplace that the Servel was the only brand "they" found to be able to maintain 40 F in the box on a 110 degree day. That place also sold Crystal Cold as well as Servel IIRC.

I remain a bigger fan of the Servel (made in Sweden) than any of the other propane models because of my burner theory.


IMO, the Sunfrost are overpriced, but some folks like them a lot. I personally do not like the chest type SunDanzer at all because I don't like to have to dig for my beer.  


After having our cabin system operational for a couple seasons I think we would have just about enough power to run a good energy efficient 120 VAC refrigerator of up to 12 to 15 cu ft.  For me to have peace of mind I'd probably want another panel or two and larger battery capacity. I have this underlying fear of us not being there, having terribly stormy, cloudy weather and running out of battery power and then having my prime ribs and gourmet ice cream melting. That would allow the purchase of a less expensive fridge and put the money saved there into the power system.

[bayview]

   We have a Norcold N-841 in our RV.   An RV refrigerator needs to be framed in on an outside wall for venting.   It operates on gas or electric.   But, needs 12 volts for the operating system.   So, hook up the gas and the 12 volts.   The 120 volt electric is not necessary to run the refrigerator.

   We use 30 lb tanks with an automatic switch-over mostly for convenience.   We refill our tanks at a service station, about a mile away. . .   

   Here is the Norcold N-841.

http://www.thetford.com/HOME/PRODUCTS/NorcoldIncRefrigerators/N841/tabid/539/Default.aspx
   
   And the installation manual.

http://www.thetford.com/HOME/PARTS/NorcoldIncRefrigerators/N64N84Series/tabid/498/Default.aspx

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[AdironDoc]

Excellent point about hauling propane and price fluctuations. Between a tankless heater, propane AC, and propane refrigerator, it would mean plenty of back and forth with the tanks. I was thinking to get a 40# (9.2 gallon?) tank which filled, weighs in at 70lbs. Still, each time I fill my small grill tank nowadays sets me back some $40. Over a summer, thats gonna run into the hundreds. Thats the price of another 200W panel.

Don and you both point out something I hadn't considered in depth. That the cost of super efficient appliances doesn't beat just putting that money into another panel and expanding the RE system. A small energy star refrigerator around 9cu/ft should be great and would be my largest draw. AC could still be propane as it's used seldom if at all. At $1.75/watt for many panels at Sunelec, I'm leaning more and more to a 400W PV setup with the Windy750 turbine throwing it's own piece into the mix. Could be I'm even oversizing a bit. I wanted 3 days power from a 50% discharge. With solar and wind, it could be much longer than that. Thus, the electric appliance vs propane begins to lean towards electric.

Once, I received an online subscription to homepower magazine. 

I picked up a copy right now. Very good read! I know what I want from Santa!

[MountainDon]

To help in the search for a truly energy efficient appliance there's loads of information at EnergyStar  They don't do propane refrigerators though, only electric.

Way down at the bottom of the list is where the most efficient fridges are listed.

[glenn kangiser]

On super insulating a standard refrigerator.... be careful as some of the fridges dissipate heat through the outer skin rather than having a radiating grid on the back.  You could not insulate it and have it work.

Some do the chest freezer conversion.

We have 2 refrigerators and 2 freezers 8ft and 24 cu ft.  We got rid of the propane one after one CO incident plus using lots of propane annually.  We are here full time though - not just weekend.  We chose to increase the size of the solar and not worry about it, however in Northern areas it might be more of a problem.

Propane fridges do not necessarily like to just start up and go right to work.  Maybe we had a bad one.  Lots of condensation and water problems inside.

[MountainDon]

Propane fridges are not self defrosting. We usually end up defrosting once through the season which for us approximately late April or early May through late October to mid November.

I've been pleased with the abilities of the Servel. It makes ice, keeps ice cream solid like a rock and I've had liquids in the fridge form ice crystals before I learned what thermostat setting worked best.


What Glenn mentioned about the skins, is a very good thing to remember. Our vertical freezer unit dissipates the heat thru the sides and top,

[glenn kangiser]

Our horizontal ones - chest type dissipate heat through the sides - Kenmore and Conserv, as does our LG fridge. 

Our 1934 GE Monitor Top however only dissipates heat through the condenser on the top and is about 4 times as efficient as any new refrigerator.  Top down is only an insulated ice box with the refrigeration unit hanging down inside from the top.  It only runs about 8 minutes per hour using around 125 watts.  Still original and running except new cord.

Pix found online like ours.

[UK4X4]

Is no one using the 12Volt fridges ?

Engel - National Luna - and a few others make 12V fridges and freeezers all designed to be run on 12v

no they are not full size double door type units but small efficient models.

Average consumption in use 1 off 80watt solar panel would cover it.

The go from 40-45ltr sizes up to 100 and some designs have dual freezer/fridge areas.

They are designed for use in vehicles and boats, but work just as well in the garage for beer ! or in an offgrid cabin.

I have an engel 45 in my truck 5 days into a camping trip after the cooler is empty I can still make ice and keep beers cold

here's an example

Actual volume
50 litres (right bin) , 40 litres (left bin) 
External dimensions
495mm (w) x 835mm (l) x 535mm (h) 980mm with lid raised
Weight Aluminium - 29kg , Stainless Steel - 31kg 
Material
Rigidised stainless steel or Structured aluminium exterior, smooth aluminium interior.
Baskets 5 x baskets standard with stainless steel models 
Power supply
12 / 24V DC, 100 - 240V AC
Power consumption *
12V - 2.5Amps average running current. 
35 amp/day average power draw.


In the US there are a few other companies making fridges as well but not sure on what compressor they use

Edgestar is one

http://www.compactappliance.com/12-Volt-Fridge-Freezers/Outdoor_Living-Travel_Coolers-Portable%20Freezers,default,sc.html

The Engel and National Luna are established as being high quality and vehicle friendly, offroad conditions and angles, the edgestar's I'm not sure

The edgestars consume a bit more current also

[MountainDon]

The only one of that type I know of here is the ARB. They are wonderful, but small for the price. I like them for off road trips but I, personally, find it too small for extended cabin use. YMMV

[Erin]

Around here you'll still see old (50s era?) Servels show up at auctions.
(At one point, my dad had 6 backups in the garage.  lol)

But he's had 2 (house fridge and beer fridge) at the cabin that have been in regular use for over 30 years.  He's started to thin the backups a little... 

So far as propane, he used to use those 100lb bottles (the size of oxy/acetalen bottles for torches and such) and plumbed them in to each appliace.
But after a few years, he found a 250(?) gallon bottle and plumbed everything together.