Solar systems and RV refrigerators

[newncguys]

Has anyone successfully powered their RV refrigerator with solar? I understand that, with enough solar panels and battery capacity, it's possible but it seems that most of the solar systems I see on places like YouTube don't come close. I made some calculations based on the GE refrigerator in the Montana (2.3 A and 276 W), 2 270Ah LiFePO4 batteries and 600W of solar. My numbers show that you could power the fridge on a daily basis, but would be left with precious little power to run much else. I'll defer to the more experienced out there; I'd love to be proven wrong on this.

 

[Mark_K5LXP]

There's more to designing solar than matching panel watts, storage and load - solar input is the dominant factor. If you're in a place that doesn't have sun, then you better have a Plan B. Even here in NM sun is no guarantee, and given the option, I would rather park somewhere with shade than roast in the sun just so my panels are illuminated (I have some solar but I don't factor it into my power budget). With stationary systems it's typical to have 3 days' worth of storage to carry you through sunless days. You can do this with your RV too but this adds to system cost with additional panels and battery. Decide up front if solar is really the solution you're looking for (extended off grid/no genset camping) and then specifically what capabilities you really need.

Mark B.
Albuquerque, NM

 

[Lou Schneider]

Take a look at the Energy Star rating for your refrigerator, it will state the estimated annual energy consumption which you can divide by 365 to get the estimated daily usage. It's less than the nameplate wattage because the compressor doesn't operate continuously.

Or you could get a $30 Kill-A-Watt energy monitor, plug the refrigerator into it and measure it's actual energy usage over a day or two. You'll probably need to use an extension cord to bring it out to where you can see the display while it's plugged in.

 

[Gary RV_Wizard]

The duty cycle on that fridge is probably less than 50%, so the actual load is something like 140 WH/hour. My 14.5 cu ft GE was closer to 35% during the day when it was warm and less overnight, so only used about 1.5-2.0 KWh/day. Individual power consumption varies a lot, though, depending on your usage habits, use of a/c inside the RV, and ambient temperatures where you camp. And then there are all the factors that Mark cited...

 

[newncguys]

There's more to designing solar than matching panel watts, storage and load - solar input is the dominant factor. If you're in a place that doesn't have sun, then you better have a Plan B. Even here in NM sun is no guarantee, and given the option, I would rather park somewhere with shade than roast in the sun just so my panels are illuminated (I have some solar but I don't factor it into my power budget). With stationary systems it's typical to have 3 days' worth of storage to carry you through sunless days. You can do this with your RV too but this adds to system cost with additional panels and battery. Decide up front if solar is really the solution you're looking for (extended off grid/no genset camping) and then specifically what capabilities you really need.

Mark B.
Albuquerque, NM

Thanks for that. I should have said that our purchase of an RV is still pending and pretty much dependent on a full answer to my question. We are searching for the model(s) we want that has an RV refrigerator rather than a residential one, but they're scarce. I totally get why the manufacturers go with residential models, but don't get why they're marketing residential fridges and solar packages in the same breath. I've been basing my calculations on 5 hours of usable sun per day but that's no more than a reasonable average. We would also have a backup inverter generator. Hopefully the members who have tried it will see my post and share their experience

 

[newncguys]

The duty cycle on that fridge is probably less than 50%, so the actual load is something like 140 WH/hour. My 14.5 cu ft GE was closer to 35% during the day when it was warm and less overnight, so only used about 1.5-2.0 KWh/day. Individual power consumption varies a lot, though, depending on your usage habits, use of a/c inside the RV, and ambient temperatures where you camp. And then there are all the factors that Mark cited...

Thank you. I made the calculation at 50% in order to be a little more ruthless with the math, but the 35% figure is more accurate. See my response to Mark for some other thoughts. Are you saying that you run your GE fridge with a solar system?

 

[Mark_K5LXP]

I think you've swerved into the deception of the marketing. Putting a solar panel on an RV and calling it solar ready is accurate in the literal definition, but probably not in the practical one without some supporting data to go with it. Just applying a caveat "may not work in all situations" if even that isn't an adequate disclaimer. Problem with that premise is that even if you press them on the details or specific performance your only option is to take it or leave it. "Fitness of purpose" is up to you to determine. I think the elephant in the room with a compressor fridge off grid is primarily batteries - having enough to carry you through a couple of days or more so you can go more than a few hours between sunless or generator-less operation. From there you can start to add sufficient solar (based on season and location) as a supplement, with the idea you're still only one day or so away from running a genset no matter what. From my perspective then the solar becomes just a nice to have because you can never really get away from a generator, or shore power. Or, decide that a retrofit propane fridge is worth the expense and trouble to install yourself. Frankly I rather enjoy being off grid for days not having to keep an eye on batteries. For many of my trips the only charging my batteries get are from the engine on the drive home. I'll be the first to say that absorption fridges aren't ideal but easy and quiet are high on the list.

Mark B.
Albuquerque, NM

 

[Kevin Means]

As a frame of reference, we started out with 960 watts of flat-mounted solar panels, and 630 AH of AGM battery capacity. Our coach is a 43 foot Class A with a residential fridge. We watch a "normal" amount of TV, we charge our phones and laptops, we brew a pot of coffee each morning... etc. If we had perfect sunlight, day after day, we couldn't quite keep up with consumption, and we had to run our generator for a couple hours every other day.

When we increased our battery capacity to 840 AH and started tilting our solar panels, we had no problem keeping up with consumption... on sunny days. On partly cloudy days, we still had to run our generator about every other day.

Now we have 1300 watts of solar on the roof, we keep the panels tilted toward the sun and we rarely have to run the generator. The only time we do is if it stays cloudy for several days, or we want to microwave something for an extended period of time. The microwave consumes a LOT of power. If we're just popping popcorn, we do that on batteries.

I think you'll find that to be a pretty close to what others experience when they're depending primarily on solar charging.

Kev

 

[solarman]

My polar N10DC uses approx 1000 W/hrs a day, in south texas weather. that unit in summer requires about 400 watts of solar, in winter only 200 Watts.
this fridge is a DC based unit optimized for low power, your residential unit will require
much more power, at your wattage value of 276 Watts and assuming 50% duty cycle a rough calculation suggests 750 Watts minimum.

 

[UTTransplant]

Another frame of reference is our rig with residential refrigerator, 900 watts of solar (3 gangs of 300 watts), and 600 amp hours of batteries. We are profligate with our power - television, charging things, espresso maker for mornings, humidifier and HEPA filter running pretty much all the time in the west. We go over night without issue. When we had lead acid batteries and no sun, two hours of generator morning and evening recharged the batteries pretty completely. Now with LiFePO4 batteries, we only need 1-2 hours a day. With solar we seldom run the generator, using it for things like running the convection oven or the clothes dryer.

 

[Gary RV_Wizard]

Are you saying that you run your GE fridge with a solar system?

I did not, since we rarely camped off-grid and had adequate back-up power for the occasional overnight. We had 400 AH of battery and a relatively quiet diesel inverter/generator.

 

[Gary RV_Wizard]

If you have a back-up generator and the freedom to use it when if needed, you can plan your system capacity for the typical sunlight and power consumption rate rather than the worse case scenario. Handle the poorer solar situations with the generator. Running the genset may be less than desirable, but maybe ok if it's only an occasional thing. Very much a personal call.

 

[LMHS]

You do have it a bit backwards. The refrigerator will run off of a battery bank. Solar panels, or a generator, are just a way to charge the battery bank.

I installed a Thomson 7.5 cu. ft. Top-Freezer Refrigerator (Model # TFR725) in my daughter's truck camper. It is powered thru an inverter by two 12vDC batteries which are charged by a THUNDERBOLT SOLAR 100 Watt Monocrystalline Solar Panel (shock, horrors, gasp! with her employee discount and a sale, the panels were far cheaper than anything I could find online). We do have a second panel that needs to be added when we add two more batteries to the roof (yes, the batteries are on the roof).

While the refrigerator runs off the BATTERIES just fine on sunny days, it's not enough to get the refrigerator thru the night during cloudy winter days. and that right there is the thing.... get thru cloudy days along with overnights. We usually use the truck camper to go to town and day trip various places. The food stuffs are removed once we get home. The refrigerator does not run 24/7. Although the rest of the camper does.

 

[newncguys]

If you have a back-up generator and the freedom to use it when if needed, you can plan your system capacity for the typical sunlight and power consumption rate rather than the worse case scenario. Handle the poorer solar situations with the generator. Running the genset may be less than desirable, but maybe ok if it's only an occasional thing. Very much a personal call.

that's very helpful, thank you. We braced ourselves for long search, fingers crossed!

 

[Runawayzy]

I have the same question and look forward to updates on your usage.