There there a optimal size for a flat room solar panel that most people get?

[JohnnyDangerDude]

There there a optimal size for a flat room solar panel that most people get or just get what happens to be on sale?

Does it matter if you get 100W, 200W, 300W, 400W, 500W, etc...? Is there like a sweet spot on a particular size?

Thanks.

 

[hwy17]

Generally as big as is practical for the application.

Rooftop panels tend to be in the 370-400W range and ground mount panels like 460-580W. 400W is about the limit of what one person could move around on their own, with difficulty. My 480's are a two person job.

Also on a roof you're often constrained by geometry so the smaller panels allow more flexible arrangement, where as for ground mount you want as big a panel as you can fit on your mounting hardware to get the most out of it.

300W and less are a niche product for mobile applications, portable use, small hobby projects, etc.

In designing a string of solar panels which is what most of us are doing, the different sizes will have different cell counts and different voltages, so they're not totally interchangeable. You might be able to use 10x 400W or 8x 480W but unable to use 10x 480W because it would be over the voltage limit.

The voltage of the panel is primarily determined by the cell count, 400W's being in the 60's and 460W+ being in the 70's or greater.

 

[timselectric]

There there a optimal size for a flat room solar panel that most people get or just get what happens to be on sale?

Does it matter if you get 100W, 200W, 300W, 400W, 500W, etc...? Is there like a sweet spot on a particular size?

Thanks.

Once you have chosen your SCC (Solar Charge Controller), then you can pick which solar panels work best for it.
Voltage is the important number. Generally, larger panels have a higher voltage.
Higher voltage panels can make it harder to hit the optimal target string voltage.

Example:
If your target string voltage is 400v.
10 x 40v panels would be perfect. But 10 x 41v panels would not. So you could only use 9. But 9 x 41v panels only gives you 369v. Which means that you are missing out on 31v for each string.

 

[JohnnyDangerDude]

Once you have chosen your SCC (Solar Charge Controller), then you can pick which solar panels work best for it.
Voltage is the important number. Generally, larger panels have a higher voltage.
Higher voltage panels can make it harder to hit the optimal target string voltage.

Example:
If your target string voltage is 400v.
10 x 40v panels would be perfect. But 10 x 41v panels would not. So you could only use 9. But 9 x 41v panels only gives you 369v. Which means that you are missing out on 31v for each string.

Looking to go full grid-tie to offset power consumption from the utility, not charge any battery.

 

[JohnnyDangerDude]

Generally as big as is practical for the application.

Rooftop panels tend to be in the 370-400W range and ground mount panels like 460-580W. 400W is about the limit of what one person could move around on their own, with difficulty. My 480's are a two person job.

Also on a roof you're often constrained by geometry so the smaller panels allow more flexible arrangement, where as for ground mount you want as big a panel as you can fit on your mounting hardware to get the most out of it.

300W and less are a niche product for mobile applications, portable use, small hobby projects, etc.

In designing a string of solar panels which is what most of us are doing, the different sizes will have different cell counts and different voltages, so they're not totally interchangeable. You might be able to use 10x 400W or 8x 480W but unable to use 10x 480W because it would be over the voltage limit.

The voltage of the panel is primarily determined by the cell count, 400W's being in the 60's and 460W+ being in the 70's or greater.

Is there a size that is more cost effective?

 

[hwy17]

Is there a size that is more cost effective?

For ground mount generally larger panels will get more wattage on the same amount of ground mount hardware so that's more cost effective.

You sort of have to look at your install and the panels available to you and the price to figure out what exactly is the most cost effective. But if you're using for example the Brightmount racks, I would want to put as big a panel as you can on it, keeping in mind they are only designed for a certain max even though they will take larger.

For me, 480's were the largest regularly available on the market and they cost quite a bit more than the cheapest panel, but my time installing the bright mount is the most expensive part for me so I knew I wanted to get the most I could out of it.

 

[JohnnyDangerDude]

For ground mount generally larger panels will get more wattage on the same amount of ground mount hardware so that's more cost effective.

You sort of have to look at your install and the panels available to you and the price to figure out what exactly is the most cost effective. But if you're using for example the Brightmount racks, I would want to put as big a panel as you can on it, keeping in mind they are only designed for a certain max even though they will take larger.

For me, 480's were the largest regularly available on the market and they cost quite a bit more than the cheapest panel, but my time installing the bright mount is the most expensive part for me so I knew I wanted to get the most I could out of it.

What about cost per watt ratio? Do you ever use that to find the most cost effective size without consideration for the mounting hardware?

I may create a mounting system using zip ties and milk crates with a bag of rocks. Ghetto style. Although that stuff is not cheap these days either.

 

[hwy17]

What about cost per watt ratio? Do you ever use that to find the most cost effective size without consideration for the mounting hardware?

I may create a mounting system using zip ties and milk crates with a bag of rocks. Ghetto style. Although that stuff is not cheap these days either.

Sure $/watt is defiantly the most used comparison in solar panels. But I would say sometimes people focus too much on it and look at more factors than that.

 

[azjeff]

ROI ratio is an important consideration to some/many.
Others, it’s insignificant.
If you have grid power available it’s a possible important consideration.
If you are off grid and presently only have power available via fuel powered sources…maybe not so much.
I got started in solar because I was in a remote area that frequently experienced power blackouts/shutdowns.
Even the local fuel station and grocery store were affected. This meant a liquid fuel powered generator wasn’t a reliable option.
My main concern was keeping my fridge working.
Keeping my food already bought from going bad.
Rethink your present routine.
Adapt to a minimalist solar lifestyle.
IMO that’s about the best you can do.

 

[wpns]

What about cost per watt ratio? Do you ever use that to find the most cost effective size without consideration for the mounting hardware?

Usually, the mounting hardware is a significant part of the total cost. Raw cost of the panels, then becomes secondary to optimizing coverage, VOC, and other factors as above.

 

[timselectric]

Looking to go full grid-tie to offset power consumption from the utility, not charge any battery.

Same thing applies to grid-tied.
Match the panels to your inverter.

 

[rogerheflin]

Usually, the mounting hardware is a significant part of the total cost. Raw cost of the panels, then becomes secondary to optimizing coverage, VOC, and other factors as above.

For my install the panels were $130, the ground mount hw was $110, the roof mount hw was about $70. Then you have wire and an inverter to run the panels/string (and whatever is needed to wire the inverter into the power system), and the inverter(s) goes from $100(all ports maxed out on big string inverter) up to $180 for a microinverter/panel.

Maxing out my big inverter would get a price of the inverter being $85/panel, the way I have it loaded it is $160/panel, and if I used micro-inverters that would be $180/panel. So probably min $400/panel for all needed parts (with a $130 panel) up to $500+/panel installed (assuming free labor).

You pick panels based on max wattage for a string (and max wattage often means lowest VOC to get the largest string size), and if you have a 420w/48v panel vs a 400w/37v panel then on a 600v string you can get 12/5040w (48v) or 16/6400w (37v), ignoring temperature compensation which would be similar on both. You also pick panels on what you can fit on your roof. Too big and you can only get a single row and waste a lot of space.

 

[TomC4306]

These are incompatible sentences.
If you're going to grid tie it's going to need to be installed to code. And inspected, and approved. I don't think anywhere in the United States zip ties and milk crates would be up to code.

Looking to go full grid-tie to offset power consumption from the utility, not charge any battery

I may create a mounting system using zip ties and milk crates with a bag of rocks. Ghetto style. Although that stuff is not cheap these days either

 

[rogerheflin]

These are incompatible sentences.
If you're going to grid tie it's going to need to be installed to code. And inspected, and approved. I don't think anywhere in the United States zip ties and milk crates would be up to code.

There are places that do not have meaningful/any inspections. My county (county population 83,000 bordering-technically part of the city's metro area-a city around 2 million--so not exactly rural) figured out a couple of years ago that not having the county officially adopt any codes had or could cause insurance issues so they adopted a building code (this learning may have been because significant tornado damage a year earlier). Their permit system is generally you just give them details of where it is going to be build and used for, but the inspections are minimal or none at all, the permit seems more so that the property assessor knows to come by and raise your property value. Ground mount panels require a permit (like a building) but roof mount require no paperwork at all, and In my state the further you move from the large cities the more lax it gets to the point that just about anything goes so long as no one gets hurt or reports getting hurt. It is all on the home owner to not half-ass it.