What are the pros/cons of using fewer higher power vs more less powerful panels?

[tab783]

I haven't been able to find a good answer for this, but cost aside, is there any benefit to using fewer larger and more powerful panels vs more smaller lesser powerful panels?

This thought is stemming from the idea that using smaller 100/150W panels on top of my RV would be easier to place than trying to cram in a few 350/400W panels. Anyone have thoughts on this?

 

[Craig]

Yes it would be fine.Other than space and having more connections both ways should output same power 3 100 watt panels = 1 300 watt panel.

 

[tab783]

Thanks for the reply Craig. That was my understanding, at least for ideal conditions.

For partial shade conditions, would there be any benefit to having a larger panel count in more series/parallel combinations vs smaller panel count either all in series or all in parallel?

 

[gnubie]

Some thoughts...

Smaller panels have more metal framing per surface area so are typically more rigid. That can be a plus for mobile installations where the flexing of the panel as the vehicle bounces along may cause cells to fail earlier than normal through cracking. That's a big may too, not a given.

The glass forms a structural part of the panel. If it's shattered the panel will become quite wiggly, the higher amount of framing for a smaller panel will mean it remains more rigid.

If a panel is shattered you will usually drop 10-15% of its output. A big panel being shattered means a lot more reduction in power production than a small panel being shattered. Likewise if something goes wrong with the panel so that it no longer outputs any power at all, you can remove a small panel from the array and not lose a significant proportion of the array's output.

Smaller panels do mean more plugs, a point of failure and if run in parallel means more inputs on the combiner box and in general more cabling.

 

[SolarRat]

"Rated" watts isn't everything. Efficiency, heat tolerance, quality, code compliant etc...The larger panels made for homes and business are usually the latest in technology and have to pass certain tests to be certified and legal (and safe) to use on a home. "12v" or "24v" panels were designed before MPPT and most probably haven't changed much over the years...not much reason to.

I'd expect a good (modern) 300w panel to produce much more power per year than 3 "cheap" (old tech) 100w panels....

 

[tab783]

I found an old video by Will that answers my question. For those that stumble across this thread in the future: "parallel as much as possible"

 

[Cajunwolf]

Buy Will's book; it's worth it. Now here's my two cents for whatever it's worth.

First, I have to agree with @gnubie on the rigidity part; those larger panels are better suited for stationary installations and way too flimsy to bounce around on an RV rooftop. Now, when it comes to shading, your much better off with several rows of smaller 100-watt panels in series-parallel arrangements like multiple rows of two or three 24 volt series pairs in parallel. This way, shading has less of an effect than it would be on single large panels. It's also easier to fit smaller panels in and around vents and rooftop airconditioning units.

 

[Tecchie]

Buy Will's book; it's worth it. Now here's my two cents for whatever it's worth.

First, I have to agree with @gnubie on the rigidity part; those larger panels are better suited for stationary installations and way too flimsy to bounce around on an RV rooftop. Now, when it comes to shading, your much better off with several rows of smaller 100-watt panels in series-parallel arrangements like multiple rows of two or three 24 volt series pairs in parallel. This way, shading has less of an effect than it would be on single large panels. It's also easier to fit smaller panels in and around vents and rooftop airconditioning units.

Can't you just use some angled aluminum to build them into a frame totally mitigating that issue? plus you'd have more points you can bolt them down with anyways?

 

[Supervstech]

Can't you just use some angled aluminum to build them into a frame totally mitigating that issue? plus you'd have more points you can bolt them down with anyways?

Well... it’s the glass size that’s the issue, not the frame mounting per-se... so unless you drill through the glass, no amount of framing would improve the strength of the glass... and I sure don’t recommend drilling holes in the panels.

 

[Ped]

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Are marginally bigger than my 160w/18v and should produce around 1.5x the current. I have room for 2 of either on my van roof. The low voltage set can produce typically 16A vs ~25A for the high voltage panels.