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How much solar do I need?
First, before you do anything else, go up on your roof and measure to see how much room you have. You should only buy what will fit on your roof. Then see what different panels have for different sizes, maybe you can fit more small ones, or, maybe you can only fit one big one.

Of course you can always buy a portable suitcase system or flexible panels and not mount them on the roof, that's another discussion.

Many people suggest you add up all your electrical use and get enough to meet those needs. But solar has gotten so cheap I say start with your wallet and buy all you can afford to spend right now. After all, if you can't  afford it, why bother finding out what your needs are? 

Also remember that you are buying for the worst day of the year--a storm that lasts for a week in the winter when the days are already short and the sun never rises very high. If you buy JUST enough for the summer, you WILL run out in the winter. Plus, you are buying for latitude, northern cities get less sun that southern cities.
Here are my recommendations. 
Minimal Power User = 100 watts. This person mainly recharge his phone, laptop, camera and a few other devices. Buy the 100 watt kit and adjust your use to it. If it's all you need, then you are done.
Average Vandweller = 200 watts. The majority of vandwellers need and can be satisfied with 200 watts. It meets all the basic needs plus, 12 volt compressor fridge, fans or even TV.I have 190 watts on my trailer and I've never been unhappy with  it. If you have the money, buy a 200 watt kit. If it's not enough, buy another 100 watt kit. Yes, you have two systems, but I consider that a blessing since you have redundancy; if one system fails you still have power. I have three distinct systems and I like it! Or, get the 200 watt kit and get the upgraded controller so you can add another one to it later when you can afford it. But controllers are so cheap now I think just buying a new cheap one is better.
Power user = 400 watts. If you have the money, start out with a 300 or 400 watt. You'll never have to worry about power even in a storm and nearly all of us can find a way to use extra electricity. I use my extra power to run a microwave and watch Satellite TV. [img=21x21]file:///C:/Users/Bob/AppData/Local/Temp/msohtmlclip1/01/clip_image001.gif[/img]
Why increments of 100 watts? Because you can get 100 watt Renogy panels cheap with free shipping. If you jump up to the big panels like 200 or bigger, they are cheaper per watt, but the cost of shipping is so high it will end up being much more. 
But, if you are near where you can get big panels and they fit your van better, get them instead.
Be aware that higher watt panels are usually higher voltage and require a MPPT controller. 
Starting with your wallet is just my personal bias, lots of people will disagree, hopefully they will speak up and explain there thinking.
2015 GMC Savannah 2500 van, 480 watts of Solar Panels--and a wonderful furry best friend named Cody. I'm out to change the world!
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The following 19 users say Thank You to akrvbob for this post:
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For people to look at the existing kits, and find out the size of the components, here are the current offerings from Renogy along with the prices.

Remember that batteries will also be needed.

This is just one component of the electrical system.
Trouble rather a tiger in his lair than a sage at his books. To you kingdoms and armies are mighty and enduring, to him they are toys of the moment, to be overturned with the flick of a finger. G Dickson.
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I like your thinking on this Bob.

I have a 75 watt panel , BUT , I bought it back in 2001 . It cost me $600 at West Marine!
And that WAS all I could afford. It was installed on a 29' class A so there was plenty of roof left to cover.

I did get a 25 amp MPPT controller so I can still get some more cheap panels to go on this 23' class C without needing an upgrade there.

I'm gonna throw out a cool idea I saw someone doing though. Panels mounted with tilting mounts on the side of the rig , some over the windows like awnings and some others on the walls. All removable to go on the ground etc when shade parking.
Stay Tuned

Weirdo Overlord  YARC CRVL edition
12 "Stinkin'Badges"  a "Full Monty Badge" 2 "Just Ignore Me" clusters  4 "Pine Cone" clusters  one "Stinkin' Badger" and 4 of the coveted "Flying Manure Spreader"awards! (What a "Stinkin' " honor !) + ROOIRIA

1981 Travelcraft Class C - 23'
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Being an engineer, I always recommend starting with a needs list (not likes or wants).  Especially if you have a medical condition that requires power for equipment (CPAP, nebulizer, refrigeration for medications, etc.).  Determine how much power your needs require.  Now you can go up on the roof and see how much solar you can fit (and measure you wallet to see how much you can afford).  If you can't meet your needs, you need to get creative or find a different solution.  And remember, you must build margin into your system for that inevitable week of rain  Sad

Other than where you start from, I think you are giving great advice.

Personal experience: I have 200W of solar and 208 AH of battery.  My big loads are a 12 volt, 2.1 ft³ refrigerator and a Maxxfan.  I am seldom below 90% battery capacity in the AM.  Additionally, I am usually up to 100% by noon on an overcast day.  My system hardly notices my charging a cell phone, laptop, digital camera or running LED lights (all on 12V, I don't have an inverter).

-- Spiff
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Are you folks using a 6V or 12V batteries? What kind of 12V fridges are you usingusing?
Thank you!
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The following 1 user says Thank You to Trekking for this post:
Bob2 (12-19-2017)
(06-01-2015, 10:01 PM)Trekking Wrote: Are you folks using a 6V or 12V batteries? What kind of 12V fridges are you usingusing?
Thank you!

I use two 6 volt golf cart batteries in series (208 amphours).

I have an old (1982) Norcold 2.1 ft³ front loading refrigerator (12V/110V).

-- Spiff
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Since this is a sticky we need to stay on topic. Off-topic posts will be deleted. Start a new thread for new topics.
2015 GMC Savannah 2500 van, 480 watts of Solar Panels--and a wonderful furry best friend named Cody. I'm out to change the world!
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Thinking of getting some solar when we get back near the family this winter. Love boondocking, but don't like to be without our electronic goodies. Right now, we're low on gas, so we have to leave the site to fill up about halfway thru our intendind stay. Well go whole hog, the 400 watt setup if we can get it on the roof. We may start now out thinking that we only want a couple lights and our devices charged, but will ease into more.
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200W works for me.  It runs my 4.8 cu ft compressor refrigerator, lights, water pump and 12V fans and charges all my electronics.  I use a very small [200W] inverter which grinds my coffee and runs my pencil sharpener when I need it [I do crossword puzzles].  When I don't bother setting up my catalytic heater, I run the furnace in the morning. It's important to get a high-quality controller.
 [Image: Updated%20sig%20pic.jpg]
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My way of thinking was to have enough panels, theoretically, to quickly replace my overnight usage; I figured an average of 3 hours usable sunlight. Then I bought enough solar to theoretically replace my overnight usage in one hour, because theory is never reality and there are overcast and rainy days. *grin*. Coupled with sufficient battery storage, another topic, it's been way more than sufficient.
"It's always darkest just before lightning scares the crap out of you."
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