How much solar do you have?

[Tom Panning]

I’m getting ready to put solar on our new 16’ Scamp, and I’m trying to figure out how much to put on. I don’t want to rely on portable panels because we’re generally away from the camper (hiking, etc) during the middle of the day, and I’d be worried about portable solar panels getting stolen. We may get a portable panel to supplement the installed panels if we’re parked in shade, but generally I’d like to rely on rooftop panels.

I’ve read enough to convince me that flexible panels are great in theory but not in practice. Our roof has the A/C in the middle plus the MaxxAir fan in the back, so there’s only room for panels in front of the A/C. I measured, and I can fit 2 panels mounted crosswise to the raised portion of the center of the roof. I can easily mount two 100 watt panels, or possibly two 150 or 200 watt panels. I plan to mount the brackets to the roof using bolts and fender washers. So what size panels are other people using, and how well does it work for them?

We want to be able to run the fridge (in propane mode), lights, water pump, etc and occasionally run the furnace if there are cool nights. We acknowledge that we won’t always be able to park in 100% sun, so having “extra” solar would help compensate. I plan to install a 200 aH lithium battery, which seems sufficient from what I’ve read.

[Perryb67]

First thing you need to do is determine what space you have on your roof for panels.

200 watt mid-sized panels need approximately 26” x 59”.
150 watt mid-sized panels need approx. 26” x 45”
100 watt compact panels need 20” x 43”

We prefer Renogy or Rich Solar panels. They seem to be the most popular right now, but there are many others out there.

As far as “How much solar do you have”:

Our 2003 Bigfoot had 150 watts and that was not enough.

Our Escape 5.0 came with 170 watts and only after we bought a 100 watt Renogy portable was that enough, but I find portables a PITA. After adding three 100 watt Renogy panels to the existing 170 watt panel giving us 470 theoretical watts we didn’t bring the portable anymore, even in shade.

Our new-to-us 2016 Bigfoot 25RQ has 160 on the roof, not enough, but with our 100 watt portable tolerable. I was on the roof measuring yesterday, and will be removing the 160 watt panel that’s in the way to add other panels. I’ll be buying two 150 watt 26” x 45” Rich Solar panels to run in series to a Victron 100/20 controller and two 24v 200 watt panels run in parallel to a 100/50 Victron solar controller, to give us a total of 700 watts on the roof. You can’t have enough solar.

Food for thought,

Perry

[AlanKilian]

I have a 30 Watt portable TopSolar panel and a controller and a 34 AmpHour gell cell battery.

It's awesome for running our water pump, interior lights and vent fan. We've never run out of juice.

I do chase the sun around the campsite since we're usually camping in the woods.

The total system cost me about US$130

[Raspy]

Perry has it right.

In this case, don't worry so much about how much you need, but how much room you have. Add all that you can, within reason, without it being shaded.

It's one thing to live very cautiously with a small system, and that is great, but adding more helps you get through days of poor weather, some shading at campsites or to run more equipment. I finally got to the point where I experimented with running an electric coffee maker and microwave, on top of my other loads and love it. Then I wanted to occasionally charge my electric bike. Then I added Starlink. And I have a 12 volt compressor fridge.

On my current trailer I started out with 380 watts of flexible panels. They were not producing anywhere near what they should because of the poor factory wiring, and shading on the roof from the AC and other things. I pulled them off and gave them away. Then I added 460 watts of glass panels and life got much better. Then I added 200 more for 660 watts total and the trailer became an off-grid trailer. What an amazing point to reach! No more plugging in under normal circumstances. Poor weather for a short period in the winter is no problem. Electric coffeemaker used every day. Fridge always on. Furnace all we want. I can even run the AC for a few hours each day if I want to.

If you upgrade to a larger solar, you must also upgrade to a battery bank that matches the solar output or the solar will be doing nothing for a large percentage of the day and you will still have limited use from your system. Mine is now at 660 watts and 480 AH of lithium. A near perfect setup for that trailer and very comfortable living.

Now, enter the new trailer I'm getting. A Roamer 1. It comes with 1,240 watts of solar and 1,100 AH of lithium. It seems like overkill, and it would never work on a fiberglass trailer because of the limited roof area, but just as an example and to demonstrate how the whole function of the system changes. It will run the AC almost all the time. It has an induction cooktop for cooking. It can heat with electric heating if the propane runs out. It has an electric compressor fridge and freezer. It will never be plugged in to shore power under normal conditions and we can camp for as long as we want in pretty much any weather. So suddenly, the trailer is more like an apartment connected to the utility in a city. This is excessive for most people, but it shows what is possible.

My theory is that usage will always rise to meet available power. Having power is very nice. Add an electric coffee pot. Charge a bike. Don't worry so much about plugging in. Camp at places with no hookups, which to me are much more desirable anyway. Leave that ridiculous generator at home, along with the weight, the noise and the extra fuel. Add a cell booster or Starlink if you want to. Add an electric blanket. Add a small microwave to defrost foods, warm dinners or for making tea.

[Tom Panning]

Thanks for the feedback. I knew on our size trailers that the question was really “how much can you fit?” more than “how much do you need?”. But it’s good to hear that 400-500 watts gets to a pretty comfortable place.

After doing some more measuring, I’ve determined that my original plan would’ve required getting too close to the front edge (the front panel would’ve gotten too much wind), but I have a new plan. I’ll have three 100 watt panels in front of the A/C, and two behind the A/C, for a total of 500 watts. And, at least to start with, we’ll bring a 100-200 watt portable panel to augment if we really need it.

Raspy, I hear what you’re saying about keeping the panels from being shaded, but on my little roof, I’d only be able to fit 200 watts far enough from the A/C shroud. Luckily, that’s the only thing casting a shadow. With my current plan, there’s a pretty good chance that the A/C will cast a shadow on one of the panels most of the time, but it can only cast a shadow on one panel at a time. Which means my system should always have 400 watts of panels that it isn’t shading. I’ll be wiring the panels in parallel so that one shaded panel won’t affect the output of the others.

[Raspy]

Tom,

That sounds very good to me. Love to see some pix when you are done. Have you figured out the wiring run yet? On mine I had to upgrade the wiring so I ran a 1/2" EMT conduit down from the roof.

[Jane P.]

Originally Posted by Tom Panning

Thanks for the feedback. I knew on our size trailers that the question was really “how much can you fit?” more than “how much do you need?”. But it’s good to hear that 400-500 watts gets to a pretty comfortable place.

After doing some more measuring, I’ve determined that my original plan would’ve required getting too close to the front edge (the front panel would’ve gotten too much wind), but I have a new plan. I’ll have three 100 watt panels in front of the A/C, and two behind the A/C, for a total of 500 watts. And, at least to start with, we’ll bring a 100-200 watt portable panel to augment if we really need it.

Raspy, I hear what you’re saying about keeping the panels from being shaded, but on my little roof, I’d only be able to fit 200 watts far enough from the A/C shroud. Luckily, that’s the only thing casting a shadow. With my current plan, there’s a pretty good chance that the A/C will cast a shadow on one of the panels most of the time, but it can only cast a shadow on one panel at a time. Which means my system should always have 400 watts of panels that it isn’t shading. I’ll be wiring the panels in parallel so that one shaded panel won’t affect the output of the others.

Tom,
I agree that roof real estate will determine the maximum solar panels you will be able to carry. However, you really don’t need more than 300-400W up there. You can actually get along with just 200 Watts - aka, a small system.

Also, wiring in serial (not parallel) will allow one of the panels to be in shade without affecting power from the other team panels. if you have an odd number of panels (five 100 watt panels), you’ll need to wire in serial. If you have an even number of panels, you’ll want to wire in serial, then parallel.

Wiring will be easier if you are installing the same size panels.

Good for you for including the space from the edge of each panel from the edge of the roof in your calculations. Also allow for space between each panel on rooftop vents and other solar panels.

I had wanted to install two 200 watt panels from Rich Solar on my rooftop. They needed to go on either side of my sunroof. But I realized those panels were 24” too wide. So, I opted for three 100 watt compact panels from HQST, wired in Serial.

But the 300 watts have meet all my needs. I am very happy with this system and so far have not missed the “lost” 100 watts.

What you should also pay close attention to is where in your trailers cabin you will be locate your solar controller, inverter, auto transfer system, and fuse block, circuit breaker & other miscellaneous fobs & components.

How many lithium batteries will you purchase (you’ll need two 100 ah or two 200 ah lifepro batteries to support a 1500-2000W inverter)? Where will you locate the batteries?

I mention this because you’re dealing with limited cabin storage.

Perry is doing an interesting thing with his new Bigfoot 25: he’s installing a 24W system. If feasible, this might be something that would work well for your trailer.
http://https://www.mobile-solarpower.com/2000-watt-24v-solar-system.html

Finally, use larger gage wiring (8 gage vs 10 gage) from your rooftop to your solar controller. (4 vs 6 gage between your solar controller or inverter and batteries It’s more efficient and safer.

[Raspy]

Originally Posted by Jane P.

Tom,
I agree that roof real estate will determine the maximum solar panels you will be able to carry. However, you really don’t need more than 300-400W up there. You can actually get along with just 200 Watts - aka, a small system.

Also, wiring in serial (not parallel) will allow one of the panels to be in shade without affecting power from the other team panels. if you have an odd number of panels (five 100 watt panels), you’ll need to wire in serial. If you have an even number of panels, you’ll want to wire in serial, then parallel.

Wiring will be easier if you are installing the same size panels.

Good for you for including the space from the edge of each panel from the edge of the roof in your calculations. Also allow for space between each panel on rooftop vents and other solar panels.

I had wanted to install two 200 watt panels from Rich Solar on my rooftop. They needed to go on either side of my sunroof. But I realized those panels were 24” too wide. So, I opted for three 100 watt compact panels from HQST, wired in Serial.

But the 300 watts have meet all my needs. I am very happy with this system and so far have not missed the “lost” 100 watts.

What you should also pay close attention to is where in your trailers cabin you will be locate your solar controller, inverter, auto transfer system, and fuse box, & other miscellaneous fobs & safety backups.

How many lithium batteries will you purchase (you’ll need 200W to support a 1500-2000W inverter)? Where will you locate the batteries.

I mention this because you’re dealing with limited cabin storage.

Perry is doing an interesting thing with his new Bigfoot 25: he’s installing a 24W system. If feasible, this might be something that would work well for your trailer.

Finally, use larger gage wiring (8 gage vs 10 gage) from your rooftop to your solar controller. It’s more efficient and safer.

Jane, It may be a problem telling someone that they can get by on a certain amount of power, just because that amount works for you. Only they know that, based on their current and future needs. I think you meant "series", not "serial". Panels wired in series are more affected by shading than panels wired in parallel. Please look at this link: https://cleversolarpower.com/shading-solar-panels/

[Jane P.]

Originally Posted by Raspy

Jane, It may be a problem telling someone that they can get by on a certain amount of power, just because that amount works for you. Only they know that, based on their current and future needs. I think you meant "series", not "serial". Panels wired in series are more affected by shading than panels wired in parallel. Please look at this link: https://cleversolarpower.com/shading-solar-panels/

Thanks Raspy, I did mean series.

I do want to respond to your comment that it may be a problem telling someone about their power needs. Tom Panning outlined his power needs: LED lights, water pump, and furnace. He plans to run his refrigerator on propane. He has a 16 foot trailer. He did not say, but may also want to power a 12V ceiling fan, audio, TV, and Medical support machine (with an adopter). All that can be handled on 300-400W rooftop solar panels.

Tom plans to purchase a 200 ah lithium. This is “sufficient” to power a 1500 - 2500W inverter. He really didn’t discuss what AC appliances he plans to support with an inverter. He also didn’t discuss whether he intends to carry a backup inverter generator.

The question Tom posed is how much solar power do “you” have. I responded: I have 300 watts, and that more than supports my off grid needs, which are actually more extensive than those listed by Tom.

Alan has a 13’ trailer & describes a truly minimalist system which meets his needs.

I would not dream to criticize you or anyone else on this forum for your discretionary spending or power consumption while dry camping. Nor can I support the idea that Tom or anyone else should cover his roof with solar panels because “one can never have enough solar” and, “because he can”.

[Shocksll]

400w all in parallel to help prevent shading issues. See my video here for more information:

https://youtu.be/5lzwRLJOBI8

[Perryb67]

Originally Posted by Jane P.

Also, wiring in serial (not parallel) will allow one of the panels to be in shade without affecting power from the other team panels. if you have an odd number of panels (five 100 watt panels), you’ll need to wire in serial. If you have an even number of panels, you’ll want to wire in serial, then parallel.

Originally Posted by Shocksll

400w all in parallel to help prevent shading issues. See my video here for more information:

https://youtu.be/5lzwRLJOBI8

Great setup!

Yes, to better avoid shading issues panels should be wired in parallel NOT series, like Jane P wrote.

Remember the old Christmas lights that were wired in series? If one light went out all the others quit working. Same applies here.

Enjoy,

Perry

[Perryb67]

Originally Posted by Jane P.

I agree that roof real estate will determine the maximum solar panels you will be able to carry. However, you really don’t need more than 300-400W up there. You can actually get along with just 200 Watts - aka, a small system.

Really? Everyone is NOT YOU. “Can actually get along” is not what most here want in their system. How do you know that other’s “really don’t need more than 300-400W up there”? I certainly don’t, but I do write in case they do.

Originally Posted by Jane P.

Perry is doing an interesting thing with his new Bigfoot 25: he’s installing a 24W system. If feasible, this might be something that would work well for your trailer.
http://https://www.mobile-solarpower.com/2000-watt-24v-solar-system.html

Finally, use larger gage wiring (8 gage vs 10 gage) from your rooftop to your solar controller. (4 vs 6 gage between your solar controller or inverter and batteries It’s more efficient and safer.

24 volt panels are more efficient than 12v panels and can easily use 10 Aug wire to the controller with less loss than 12v panels using 8 awg wires to the controller. It’s not just “feasible, but done quite often today once people understand the electronics involved to get better solar harvest from your roof. You do need a MPPT controller though.

Originally Posted by Jane P.

I would not dream to criticize you or anyone else on this forum for your discretionary spending or power consumption while dry camping. Nor can I support the idea that Tom or anyone else should cover his roof with solar panels because “one can never have enough solar” and, “because he can”.

I don’t see anyone here “criticize” for other’s lack of discretionary power, so don’t see a need for your first sentence.

Solar is like 2-Footitis. At some point many want more, and realize “one can never have enough solar”. Of course, if one accepts barely enough to camp that’s fine, but like 2-footitis many will agree with never having enough. As people camp more often they seem to bring more electrical items with them. I don’t write specifically for me or you and write to help more than just the OP. So I still will write, “you can’t have enough solar.”

Ironically, we’re heading to friends in Tucson today to charge our SOK batteries with only 260 watts available, because it’s too cold in Arizona for lithiums to sit outside in our Bigfoots battery bay when the temps go below 34F (SOKs charge shutoff) and have to wait until 41F to start charging again (SOK’s charge turn on). The past few days it’s been around 21F in the morning at Cochise Stronghold and Chiricahua National Monument. We also have shade half the day for our rooftop at Chiricahua.

In this situation the batteries haven’t reached 41F till noon or later. We only have 160 watts on the roof and a 100 watt portable and we’re losing about 20 ah’s every day. Therefore, with 260 watts we don’t have enough solar (no, we don’t currently have an inverter). It happens to everyone that has barely enough for most situations, but soon or later they find they don’t have enough.

If we still had our Casita I can guarantee you that we would put a minimum of 400 watts on the roof, and it can be done. Everyone makes choices and I’m happy 300 watts currently works for you. I write for others though.

Enjoy,

Perrry

[Jon Vermilye]

2 160 watt panels on the roof that I tilt in the winter, and a portable 300 watt flexible panel for which I built a 3/4" PVC pipe frame and add when necessary (usually only in the dead of winter or when parked in the shade).

[Raz]

Sixty watts. Two thirty watt panels hinged . Lights, water pump, fan. Here in the north east, most campground sites are shaded, making solar questionable. In full sun, sixty watts charges my battery in about 4 hours. I can go three days without recharge and I made a cable to plug into my 7 pin with the battery in the bed of my pickup. Lets me recharge while out and about.

[AlanKilian]

Originally Posted by Raz

Sixty watts. Two thirty watt panels hinged . Lights, water pump, fan. ... I can go three days without recharge

Wow! That just about exactly matches our experiences here in MA.

I like camping, we mostly sleep in the tent and use the Scamp for evening sitting around playing games and when the weather is nasty, so we're not going to have a lot of electronic stuff and we do enjoy ourselves!

[Tom Panning]

Thanks everyone for the data, there's quite a spread! It looks like my plan for 500 watts will be overkill for what I "need" (propane fridge, lights, water pump, and ceiling fan or furnace depending on the temperature). Everything I "need" can run on 12V, so I'm not going to install an inverter right away. We need to be able to do this for two weeks straight in tree cover. We're planning to spend two weeks without electrical hookups at Sequoia and Kings Canyon NP this summer (we also have shorter stays without electrical hookups leading up to it, so we'll have a chance to practice and get a feel for the system's productivity). Also, dealing with even a small generator would be kind of a pain for us. We could do it if we have to, but if we can get everything through solar I would much prefer that.

Of course, what I want is something more. Being able to use the microwave would be nice (which would require adding an inverter). If we could occasionally run a slow cooker, that would be nice too, although that can definitely use up some watt hours. If we have enough solar and battery that we only feel the need to hook up when we need an air conditioner, then that would give us a lot more options for camping. We generally prefer state and national parks, but we've often stayed at private campgrounds just for the electrical hookup. I'm willing to "overbuild" the solar panels if it would put us in that position. Besides, the difference between 300 watts and 500 watts is under $300, which would pay for itself in the first year just in reduced camping fees.

As for where we're going to put the battery, solar controller, etc. I checked, and the best option is under the port bench of the dining table. We have a Scamp 16 Deluxe, Layout 6 (with the wet bath and front bunks). I wish it would fit under the bottom bunk in front, but there's not enough room for the batteries and not enough ventilation for the solar controller. The solar panel wire is pretty straightforward: it will go through the roof into the cabinet above that bench, and then run down in the corner up against the fridge and microwave wall.

I'll make sure to post pictures of the solar panel layout and the electrical compartment when I'm done, but that will be a couple months away.

[Gerry]

we run 100 w panel with a gel Battery and have been out for 2 weeks in the National Forest in NH with no problems. Portable panel does have to be moved a few times a day to catch sun as it comes in different spots on our campsite. Plenty of power to run lights, to read at night or cook, water pump to take showers, and furnace if nights are cool.

[Raspy]

Tom,

Two points you probably already know, but here goes:

The collector's rated power is not what you will be getting with them mounted rigidly to the roof. 60-75% is more realistic, under ideal conditions, and hoping for 75% probably won't happen.

AC is extremely power hungry and way out of reality with a small system of only 500 watts. You can approach this problem in a couple of ways. Get the AC off the roof to make more room for panels and go to a smaller AC unit, mounted somewhere else, that is still big enough to do the job. On my order, I deleted the AC which was rated at 13,500 BTU because it was too big physically and too high of a BTU output, which meant a higher energy draw than was needed. Then I installed a much smaller output window unit through the back wall. I also have a Maxx Fan where the AC would normally go and really like it.

I don't know just how long I can run the AC from the batteries and solar, but for sure several hours a day, day after day. And if I won't need it the next day, I could easily double that. I went to an 8,000 BTU unit and wanted a smaller one, but that was the smallest in a vertical format unit I could find. My trailer is very well insulated, but it still runs less than half the time. A 5,000 BTU would have been a better match for the trailer.

Remember too, the inverter efficiency is only about 90%, so when running a 120 volt AC, 10% of the battery power is wasted as heat. And further still, Lead acid/AGM batteries produce lower and lower amounts of power the higher the amp load, and cannot be run lower than 50% of their capacity without severely shortening their life. For best performance, be sure to get lithium batteries.

I'm glad you are willing to "overbuild" your solar system as you are already looking forward to wanting more power for improved camping opportunities, lower fees, and more convenience items. For what it's worth, remember my theory: Usage will always rise to meet available power.

Looking forward to your pictures.

[Raspy]

Originally Posted by Gerry

we run 100 w panel with a gel Battery and have been out for 2 weeks in the National Forest in NH with no problems. Portable panel does have to be moved a few times a day to catch sun as it comes in different spots on our campsite. Plenty of power to run lights, to read at night or cook, water pump to take showers, and furnace if nights are cool.

It is fun to camp more minimally than most. I like the 100 watt portable panel I have too. But to be fair, 100 watts of portable power, that can be aimed directly at the sun during the day, is not the same as 100 watts of panels mounted flat on the roof. The portable will easily outperform the flat panels. Test show it will produce about twice the power per day if aimed carefully. So, 100 watts of portable can be roughly equal to about 200 watts of flat roof panels, in overall performance per day. It would be a mistake for someone to think they can mount a 100 watt panel flat on the roof, and have the same performance as a 100 watt portable that gets aimed at the sun.

[Shocksll]

Originally Posted by Raspy

Tom,
I don't know just how long I can run the AC from the batteries and solar, but for sure several hours a day, day after day. And if I won't need it the next day, I could easily double that.

I tested how long I could run my 13.5k btu A/C. Spoiler alert, it was over 3 hours.

https://youtu.be/q_xuuSf26eg