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Old 10-14-2021, 07:50 PM   #1
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Why are 100W panels so common?

Ever notice that about 90+ % of the skoolie solar systems use 100 to 175watt panels? Yes I know residential and commercial panels are larger but with very reasonably priced 250 to 350+ watt panels available, that would also easily fit oriented across the width of your bus (side-to-side) verses in line front to back.
The price per watt when comparing the two size ranges is in favor of the larger, higher wattage and in most cases more efficient panels.
To illustrate the point, total the foot print of ten to twelve 100 watt panels, verses four 300 watt panels. The latter leaves plenty of room for a rooftop deck.

Educate me. Is there a reason behind it the popularity of the low wattage panels?

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Old 10-14-2021, 09:37 PM   #2
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Are you going to make a wing? I’ve seen some builds where, because of the curve of the roof, there is significant space between the panel and the roof. Never looked right to me
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Old 10-14-2021, 09:38 PM   #3
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Quote:
Originally Posted by ddwbeagles View Post
Ever notice that about 90+ % of the skoolie solar systems use 100 to 175watt panels? Yes I know residential and commercial panels are larger but with very reasonably priced 250 to 350+ watt panels available, that would also easily fit oriented across the width of your bus (side-to-side) verses in line front to back.
The price per watt when comparing the two size ranges is in favor of the larger, higher wattage and in most cases more efficient panels.
To illustrate the point, total the foot print of ten to twelve 100 watt panels, verses four 300 watt panels. The latter leaves plenty of room for a rooftop deck.

Educate me. Is there a reason behind it the popularity of the low wattage panels?

I think there are a few reasons:
1. People have become very used to buying from either Amazon or a Big Box hardware store, ~100w are vastly more common
2. As a generalization, there isn't (yet) a great depth of knowledge in this community when it comes to solar, of course there are many exceptions to this, and it is changing, but as it is, its pretty shallow. That leads people towards the solar products that are actively marketed towards them, whether that is explicit marketing/advertising or indirectly through youtubers, etc.
3. They are easier to handle/maneuver/install if you are doing it yourself (solo)
4. Many people dont really know where to look for the big panels, retail sales is often an afterthought of non-existant when it comes to residential panels.
5. Shipping can be a bitch with the large panels
6. Its easier to make the little guys fit the contour of the roof




Just my 2c / speculation, nothing wrong with the smaller panels, and there can be advantages, but as you mention price per watt is usually heavily in the large panels favor if you know where to source them.
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Old 10-14-2021, 09:40 PM   #4
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Consumer panels are driven by cheap price and retail distribution / shipping issues.

Note also voltage too low to get the efficiency increase from MPPT

Ideally 40+ Voc
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Old 10-15-2021, 07:33 AM   #5
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We have six 305-Watt panels, a total of 1,830-Watts.
.
We acquired these from a re-fit after new panels were installed on an office building.
.
Although we trundle up rough logger tracks to remote mountain lakes, and across trackless deserts to isolated Baja beaches, I am concerned about bouncing and vibration cracking the glass... but, so far, they seem indescribable.
They are unfazed busting through low branches.
They may outlive the Union!
.
Our panels are awkward, yuge and heavy, compared to a 100-Watt.
Mounting them, we used a fork-lift with an enclosed worker-platform.
I think smaller panels have advantages.
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Old 10-15-2021, 07:58 AM   #6
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I ask myself that also. I think they just copy of each other. I have two 360W REC Solar panels. I was able to toss them up there my self and only have to mount 8 brackets to roof so the less holes in the roof the better. My panels sit right tight to the roof.
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Old 10-15-2021, 01:15 PM   #7
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Great panel wattage feedback

Lots of great feedback and tons more research to do but a couple of points to make. I think the lower voltage concern can be mitigated through panel wiring (series or series parellel) as as long as it is 20% greater than the voltage of your battery array you should be OK. Again, that's my early understanding.

Next is the overhang. Typical size for even the 400w+ panels is around 80"L x 40"W. The bus width is close to 8'. So 40" away from the bus' centerline I suspect my panel edge elevation will only be a few inches and thus should be aesthetically appealing and zero overhang whether I mount them lengthwise across the width of the roof or run mate two together (side-by-side) running butt to to nose of the bus. Same 80" dimension.

dzl - Loved your response and think you nailed it. The entire process is still very grey to me and we haven't even talked about 12v, 24v vs. 48v systems. But I see I am in the right place and appreciate the advise, responses and feedback.
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Old 10-15-2021, 01:37 PM   #8
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I think there will be times I want to walk on the roof, wide panels make the roof useless for anything else.
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Old 10-15-2021, 03:53 PM   #9
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Are you going to make a wing? Iíve seen some builds where, because of the curve of the roof, there is significant space between the panel and the roof. Never looked right to me
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Old 10-15-2021, 06:05 PM   #10
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I think it also depends how big of a system you want or need. I have 4 100 watt panels and that has done everything I have wanted. I do have one more panel and may at some time put it on. Also for me I put a large canoe on the roof, so large panels would get in the way of that. Use what suits your needs.
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Old 10-15-2021, 09:06 PM   #11
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Solar Wing

Not sure I know what a solar mounted "wing" is. Still early in the game but would like to see if I can mount them in a frame so they sit off the rood but as close to the roofline as possible. Would love to have one side of the panel mount tilt able (either manual or pneumatic) but I'll cross that bridge later.

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Old 10-15-2021, 11:04 PM   #12
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With a curved roof, wings means the panels' vertical gap to the bus roof increases toward the side edge,

if you go out to the full wall line width, might be 8" or more than in the center.

High lifting force at highway speeds, panels may take off, while the bus stays on the ground.

Some think the solution is those "semiflex" type, can be done but 5x the price and 1/5 the lifespan, and also lots less efficient conversion per square meter.

A square roof profile like a connex or truck body would be a better solution, get a full 7.5 - 8' width and still have room for some HVAC intrusions.
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Old 10-16-2021, 01:16 AM   #13
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A 100 watt panel is basically a 12 volt panel. You can string them together for more voltage. It's a form factor issue. Fewer big panels, or more small panels.

Kind of a dilemma: more sail area or more connections/penetrations.
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Old 10-21-2021, 03:31 PM   #14
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Quote:
Originally Posted by ddwbeagles View Post
Ever notice that about 90+ % of the skoolie solar systems use 100 to 175watt panels? Yes I know residential and commercial panels are larger but with very reasonably priced 250 to 350+ watt panels available, that would also easily fit oriented across the width of your bus (side-to-side) verses in line front to back.
The price per watt when comparing the two size ranges is in favor of the larger, higher wattage and in most cases more efficient panels.
To illustrate the point, total the foot print of ten to twelve 100 watt panels, verses four 300 watt panels. The latter leaves plenty of room for a rooftop deck.

Educate me. Is there a reason behind it the popularity of the low wattage panels?
Ruth and I often wonder the same thing, but we realize our goals are different. We have twelve 327W panels on the roof and are considering going up to 450W panels. Real estate on the roof and cost of panels is what made us choose the 337W panels. Our goal is to live like we are plugged into the grid but not be.
We got our panels for less than 150 each. Now we are seeing 450W panels for around 200. Its getting attractive. Last year we only ran the generator for a total of 48 hours out of 8760 hours of electrical consumption, so we are really close to our goal.
I suppose that some folks dont like the aesthetic of huge solar panels on the roof. I c az n say that the reaction we get from people who see them is always positive.
Choose your panels based on the power goals and space you have to mount them.
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Old 10-21-2021, 03:34 PM   #15
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Originally Posted by john61ct View Post
With a curved roof, wings means the panels' vertical gap to the bus roof increases toward the side edge,

if you go out to the full wall line width, might be 8" or more than in the center.

High lifting force at highway speeds, panels may take off, while the bus stays on the ground.

Some think the solution is those "semiflex" type, can be done but 5x the price and 1/5 the lifespan, and also lots less efficient conversion per square meter.

A square roof profile like a connex or truck body would be a better solution, get a full 7.5 - 8' width and still have room for some HVAC intrusions.
If you mount them correctly you have no worried.worries. our house is our car. We have 25 thousand plus miles with 12 huge panels on the roof of our bus and never a lift off or even an indication of a try.
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Old 10-21-2021, 03:40 PM   #16
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I think there will be times I want to walk on the roof, wide panels make the roof useless for anything else.
We have 12 327W panels mounted with a path down the center so that I can do just that. We are starting a new build in which the path is going to be deleted. We just dont find the need to walk up there as much as we imagined when we mounted the panels the first time.
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Old 10-21-2021, 03:42 PM   #17
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Are you going to make a wing? Iíve seen some builds where, because of the curve of the roof, there is significant space between the panel and the roof. Never looked right to me
You would probably really think ours doesn't look right, however we have never taken flight.
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Old 10-22-2021, 09:28 AM   #18
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We are starting a new build in which the path is going to be deleted.
I look forward to seeing what you guys do. I'm thinking of a new build early next year, although now sure if I'll start on a bus chassis. Researching tiny homes and super-Cs at the moment,but before my hope was on a coach.

As for wings... because my panels are a full 6" off the roof I think it doesn't catch air as much as it allows air to pass under. I did cross 6 states with the panels flat up there like that, so its probably fine. I do want to close off the sides when I do slide outs, if the slide out system even happens (new build = no need).
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Old 10-23-2021, 12:26 AM   #19
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Are you going to make a wing? Iíve seen some builds where, because of the curve of the roof, there is significant space between the panel and the roof. Never looked right to me

We will be using high watt panels in the 380-400 watt range. We will install four rails the entire length of our roof and the panels will be mounted to those rails. Yes, they'll have an air gap and that is AN ADVANTAGE because it will ONE keep panel temps lower than if mounted with low or no air flow under them and TWO will offer a sun shade to the roof which will eliminate solar heating through the roof.
A flat plate perpendicular to air flow does not create any lift. Nor does a panel with minimal Angle of Attack if there is an air damn at the front.
Becoming a "wing" is not an issue when properly installed.


As for the amount of space taken up, even the largest panels in this range will allow a 14" walk way between the panels which is necessary for snow removal, washing, etc. and that's without going beyond the existing width of the bus walls.


For our use, any rail space not covered by panels will be covered by wood or another solar impenetrable material so that the entire roof minus vents and hatch are covered for maximum solar shielding of the roof.
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Old 10-23-2021, 12:27 AM   #20
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Quote:
Originally Posted by Rock-N-Ruth View Post
We have 12 327W panels mounted with a path down the center so that I can do just that. We are starting a new build in which the path is going to be deleted. We just dont find the need to walk up there as much as we imagined when we mounted the panels the first time.

I'm curious about how you clear snow dust/dirt etc. without going on the roof? That's the only reason we plan for a center walkway.
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