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Ask Dave: Can I run a residential fridge on 190w solar panel and a battery?

Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club. Today he discusses running a residential fridge on a solar panel and battery.

Running a residential fridge on solar

Dear Dave,
I just picked up my first trailer, a Wildwood FSX 179DBK. It has a two-burner propane stove, microwave, and a fridge, but no oven. Not knowing any better, I assumed the microwave was also a convection oven but, surprise, it is not. I thought the 11-cubic-foot fridge was a dual-service fridge. During the inspection, my inspector found it was not but it has a 300-watt inverter connected to a 12-volt line. He also pointed out that none of the 110v outlets will work unless I am connected to shore power or to an inverter generator.

Questions: Is that normal? Am I better off changing our fridge to a 12v or a dual propane/electric fridge? I was planning on boondocking Nov.-Feb. near Phoenix, AZ, with a 190w solar kit on top of the RV. Is that setup on one GMS battery enough? —Randall

Dear Randall,
To start with, your Wildwood is not set up to boondock very well as most of the appliances and outlets you have are 120-volt dependent. Plus, a 300-watt inverter and one battery will typically only power the TV. If you plan to boondock for four months, you will need to evaluate your amp-hour requirements and upgrade your batteries, inverter, and solar panels. If you want to use the outlets for the 120-volt operation of items like a coffee maker or to charge computers or other items, that will need to be supplied by an inverter as well.

Figure out the power draws

Step one is to identify what AC and DC draws you will have and how often you will have much more than just your refrigerator running down the batteries through the inverter. Visit Go Power!, where you will find a list of common AC and DC appliances and what they typically draw. This worksheet also has formulas to calculate the number of hours you think each appliance will run per day and get approximate total amp-hours per day.

solar sizing worksheet

For example, an AC refrigerator is listed as 10 amp and you will need to calculate how long it will run each day. This will be determined by the ambient temperature in your rig. However, the side note to this is they are rating a 4-cubic-foot refrigerator. Most RVers will be using a much larger unit that could draw 30-40 amps.

Other 120-volt AC appliances that might be powered by the inverter and drain the house batteries are the microwave at 100 amps, TV at 4 amps, and computer at 25 amps. 12-volt DC appliances or functions that will draw directly from the house batteries include lights, vent fans, water pump and more. Hopefully, you have LED bulbs as they draw one-tenth the power at about .05 amps. Other items include roof vent fans (4 amps), and water pump (4 amps). Even your LP appliances such as the water heater, stovetop, and furnace will draw 12-volt house battery power, especially the furnace fan at about 8 amps.

Calculate power usage for amount of time

Next, you will need to multiply the total amp hours you estimated by the number of days or weeks you plan to boondock, which in your case is four months. Then match your solar panel size, inverter, and battery needs. Go Power! also has a quick guide showing different RV configurations and days out that shows a travel trailer about your size would need 380+ watts of solar panels, 2,000-watt inverter and 400 Ah+ if using AGM and 200+ Ah if using lithium, as they can be drawn down to almost 100 percent of available amp hour capacity.

solar kits by RV type

Not a perfect science!

Even armed with all this information, it will be just an estimated guess and none of us can truly calculate how long the refrigerator will run, the lights will be on, or how often the furnace kicks in. And what about cloudy days? I do recommend adding portable solar panels to your system as they can be placed out in line of sight to the sun while your trailer is parked under shade to cool it down. Arizona does get a little hot even in the winter. If you are boondocking, you won’t be able to use your roof air conditioner. Parking in the shade can cool the rig down 20+ degrees, but you get no sun to your roof-mounted solar panels.

RV in shade, solar panel in sun

Another good source of information on solar panels and systems is Zamp Solar, which along with Go Power! is now owned by Dometic. And as always, when it comes to calculating electrical needs I would recommend reading Mike Sokol’s articles.

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chris
25 days ago

Whenever anyone asks if their solar can “run” something, I know they’re very new to the game.

Last edited 25 days ago by chris
Mike
25 days ago

Hmm. This article says that a microwave will take 100 amps. How is that possible when it is plugged into a 15 or 20 amp plug? Same with the fridge. Can’t draw 30 to 40 amps on a 20 amp circuit.

Glenn
22 days ago
Reply to  Mike

100 amps on the 12v side of the inverter to provide the 120v to run it.

Jeff Craig
28 days ago

You’ll forgive me, but this is a case where product research and a better salesman would have helped. The 11CF Dometic fridge runs on 12V per the Forest River website, so a 300w inverter wouldn’t be needed for the fridge, just an LED TV (and that would indicate at least one outlet is wired for the inverter) next to the microwave. I hope this camper also realizes the cooktops exhaust vent blows out over the microwave, not to the outside of the Trailer.

Crowman
28 days ago

Buy a 2000 watt generator and your problems solved.

Tommy Molnar
29 days ago

I never really did one of those power use calculations when I was setting up our trailer. I just know “more is better” when it comes to solar panels. You don’t really have to be in direct sunlight for solar to work, but the more panels you have, the more recharging you’ll experience even in a shady area. Same thing on a cloudy day. I think I agree with Bob P’s last sentence.

Bob P
29 days ago

A classic example of no research before buying, anything that costs more than $100 requires research, research, and more research. His unit will be up for sale before long when he finds out much it’s going to cost and how much work will be involved.

Don
29 days ago

Excellent response, Dave! It amazes me to learn how naive many people can be regarding power requirements for boondocking. This detailed reply may help reduce that confusion…

Irv
29 days ago
Reply to  Don

+1

Jeff Craig
28 days ago
Reply to  Don

+2!