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Electric only refrigerator experience
Early last fall the boiler tube of my stock Dometic 2 way fridge failed 36 hours before I was to leave on a multi week cross country trip. (There is nothing like the fresh and overpowering smell of ammonia and a large puddle of yellow liquid under the fridge to start your day off right:). In the ensuing scramble and improvisation I ended up with a residential Hisense 4.4 cu. ft., 2 door refrigerator purchased from the local Costco for $169.00. The unit was plugged into the power inverter on a Goal Zero(GZ) 1000w solar generator that I already had available for power. (The GZ was plugged into a 12 volt outlet under the dinette table for charging.) My solar charging setup includes a factory installed 100 watt roof panel and solar controller  plus 2/100watt portable panels that are direct connected to the 2/6 volt, wet cell house batteries with a separate solar controller.) This set up worked well enough for me that I am going to continue it through the summer months to gain additional data before I decide whether to stay with electric only or buy a replacement 2 way RV fridge. I thought I would share a few things I have learned from this experiment to date:

1) While leveling is obviously still important it is definitely less stressful during travel, longer daily stops etc. as is remembering to turn gas on/off for refueling, while traveling etc.
2) Items placed in the freezer stay consistently hard frozen.
3) Incorporating  a modest sized portable solar generator into the power mix may work for some applications from the standpoint of both cost to integrate and enhanced power flexibility.
4) Finding residential refrigerator/freezers that use all of the existing opening is a challenge. There are many different options in the 4 cu. ft. range that fit with plenty of room to spare  but 5,6 and 7 cu. ft. are just about impossible to find(at least for me).
5) I tracked the energy used by  the electric refrigerator I purchased very carefully using the power meters built into the GZ across multiple days and found that the ratings listed on the yellow Energy Guide certificate that was included with the unit was actually quite accurate. Therefore, I believe that these certificates could be very useful for individual energy use comparisons. The attached pics are of certificates I used for one analysis. The first is for the 4.4 cu. ft. unit that is currently installed and the other is for a 6.9 cu. ft. LG unit  that I might consider as a longer term replacement:

Hisense 4.4 cu.ft. - standard compressor
328 kWh/yr. = 328 x 1000w = 328,000w/365 days = 898w/24hr=37watt/hr.

LG 6.9 cu.ft - inverter compressor
220 kWh/yr. = 220 x 1000w = 220,000w/365 days = 603w/24hr=25watt/hr.

6)   The LG is 1/3 larger but uses 1/3 less power most likely due to the
      inverter compressor configuration.
7)   I did end up running the generator for charging purposes a couple hours each month which
      didn’t exceed the hour or two with load monthly maintenance run that I would have
      performed anyway.
8)   Be sure to take into account the power used for any energy conversion. For example, the
      inverter on the GZ 1000 draws 4 watts/hr. X 24hr. = 96 watts. I also have a GZ 1500 with
      a larger inverter that draws 9 watts/hr. X 24hr. = 216 watts. Either could easily power the
      fridge.

Unexpected circumstances led to this experiment but I have learned quite a bit as a result. I’m looking forward to the final phase.

Happy Trails!

Matt
    


2004 26.5 Island Bed. Gumby
2006 Jeep Wrangler Rubicon
Re: Electric only refrigerator experience
Reply #1 –
Norcold has a drop-in  8-cu/ft 12-volt compressor refrigerator.
Norcold N8DCSSL RV Trailer Camper 8 Cu Ft Dc Compressor Refrigerator NEW | eBay

We have run a 40-qt compressor ice chest continuously for 18 months strictly off solar only.
Next time the refrigerator dies, it will be replaced with a compressor model...I'll do almost anything for hard ice cream.

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Electric only refrigerator experience
Reply #2 –
We plan to drive to Indiana and having JC Refrigeration to convert our Dometic 2652 to a 12v DC compressor fridge.
2004 Mid Bath,
2007 Jeep Liberty Towed
Re: Electric only refrigerator experience
Reply #3 –
And speaking of hard ice cream, note the following in that LG refrigerator's product description:

"The LG 6.9 cu. ft. Single Door Refrigerator, Model # LRONC0705V has a freezer compartment that is designed for making ice and for short-term storage of already frozen food. The temperature in the compartment may not get cold enough to freeze fresh food or to store foods such as ice cream safely."

That aside, if you're going to go electric, why put up with the inefficiency of inverter conversion from 12 V to 120 V? Why not get a true 12 V fridge--the type designed from scratch for marine and RV use? (E.g., Vitrifrigo DP150.) From what I've seen, these are more efficient than residential fridges, whether running from 12V or from 120 V (they will switch over automatically if AC is available). I've had DP150s in two rigs now, powered by solar panels in both cases, and was very happy with them. (I'm now using a smaller Vitrifrigo C130, which is all that will fit in my 19' Airstream.)

Maybe residential fridges are less expensive; I haven't compared prices. That could be a reason to favor them. But I'm pretty certain that they are not as efficient overall.
Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"
Re: Electric only refrigerator experience
Reply #4 –
Larry and Andy thank you for the excellent comparables. I found the energy use data for each listed in watts and/or I converted from listed amps to watts. (Hopefully I converted correctly.)

Vitrifigio 150  5.3 cu. ft. nominal power draw is listed as 31 watts.

Norcold N8DCSSL 8.0 cu. ft. power draw range is listed as 44 watts - 68 watts

LG 6.9 cu. ft.  Energy Guide estimate 25 watts plus 4 watts inverter is 29 watts

If I'm doing the calculations correctly isn't the LG energy use similar?

The LG costs around $550 and will soon be available at Home Depot and  Best Buy. Both the Vitrifigio and Norcold appear to be  in the $1500-1800 range when shipping is included.

All analysis aside I'm a purist like Larry when it comes to ice cream......:)

Great discussion and information. Thank you so much.

Matt





 
2004 26.5 Island Bed. Gumby
2006 Jeep Wrangler Rubicon
 
Re: Electric only refrigerator experience
Reply #5 –
"If I'm doing the calculations correctly isn't the LG energy use similar?"

If I had to guess, I'd say "Probably...?"

But comparing refrigerator power specs can be tricky. I believe that the Energy Guide number, for example, is based upon "average" usage, where average is defined as some standard test condition--for example, with the compressor running half the time. In a quick search, I wasn't able to find out just how it's calculated.

Vitrifrigo doesn't use Energy Guide labels. (Maybe they're exempt because they're selling mainly into the marine market?) They specify the DP150's "nominal consumption" as 65 watts, but it's unclear what they mean by "nominal," and I found retailer sites giving the 31 W number that you mentioned. That leads me to suspect that the DP150 draws 65 watts when running, but overall is more likely to use about half that much at a 50% duty cycle.

Hmmm... there ought to be a way to verify that. Well, by my measurements, my Vitrifrigo C130 draws a little less than 4 amps when running--around 45 watts. And Vitrifrigo's specs for that model say that its "nominal consumption" is 45 watts. So that tells us Vitrifrigo's "nominal consumption" is power consumption when running, not overall average consumption. (Why they threw in the word "nominal," I don't know. It just confuses things.) That explains the 31 watt number we're seeing elsewhere for the DP150: as I'd guessed, it must be based upon a 65 watt device running with a roughly 50% duty cycle.

I'm not sure what to make of Norcold's 44 to 68 watt range. Judging by the other fridges we've talked about, that's probably power consumption with the compressor running, so at a 50% duty cycle it would be more like 22 to 34 watts--but that's just a guess on my part.

The point is that when manufacturers (or the FTC) calculate "average" power, factors such as duty cycle make comparisons between brands difficult. Of course that's what the Energy Guide labels are supposed to work around, but not all brands carry those labels.
Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"