4 Advice to Choose a 144 Cell Solar Panel

If you're looking to switch to solar, you may wonder if you have enough space to install the panels. This is a valid concern - solar panels are pretty big! Most home solar panels are about 5.5 feet x 3 feet and weigh roughly 40 pounds each.

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Most of the time, you won't see the size of solar panels expressed in feet. Instead, you'll see it's listed as the number of solar cells within a panel, with the most common solar panel sizes being 60-cell and 72-cell.

Let's take a closer look at the difference between these solar panel sizes and how to pick the right one for your home.

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How to measure solar panel size

When you look at a solar panel, you’ll see it’s made up of small squares. Those squares are called solar cells, and they're the part of the panels that turn sunlight into electricity.

You'll see the size of a solar panel described by how many cells it has. 60-cell panels are usually laid out in a 6 by 10 grid and are the most popular option for home solar installations. You’ll typically find that 60-cell solar panels have output ratings between 350 and 400 watts and efficiency ratings between 17% and 19%.

72-cell panels, on the other hand, are usually arranged in a 6-cell by 12-cell grid. Because 72-cell panels hold more cells, they are bigger and can produce more solar power, making them popular for commercial installations. 72-cell panel wattage usually sits around 415 to 450 watts, but they can get into the 460-watt range. Their efficiency ratings are typically between 18% and 21%.

Solar panel dimensions and weight

Many people want to know the physical size of solar panels, not just how many cells the hold. The average 60-cell solar panel is about 65 inches by 39 inches, or 5.4 feet by 3.25 feet, and weighs around 40 to 50 pounds. The actual dimensions will vary from panel to panel, so we’ve listed a few for some of the most popular 60-cell panels on the market:

72-cell panels are larger, about 80 inches by 40 inches and about 1.5 inches tall. This works out to just about 6.5 feet by 3 feet for 72 cell panels, give or take a few inches. 72-cell modules generally weigh around 50 pounds. Here are the dimensions for 72-cell panels offered by top brands:

Pros and cons of 60-cell and 72-cell solar panels

Here’s a brief breakdown of the pros and cons of each panel size.

How big are portable solar panels?

Once solar panels are installed on your roof, you don’t have to think much about their size anymore. 

But, with portable off-grid panels, solar panel size is one of the most important things to consider. Your RV might only have a small amount of roof space, or you might want something you can carry around and set up outside your campsite!

Because portable solar panels are made for travel, they tend to be smaller and have about 40 cells as opposed to 60. 200-watt portable panels are around 5 feet by 2 feet. 

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You could also opt for flexible solar panels, which also measure about 5 feet by 2 feet. But flexible panels can bend and are much thinner than crystalline panels, so they’re easier for storage.

The flexible panel sold by Renogy, a popular portable solar brand, has 72 cells, but they’re smaller than the ones used in typical commercial panels. The panel is also substantially lighter, weighing just 10.8 pounds!

Folding solar panel kits are also an option for portable use. Foldable panels can be small enough to fit in your backpack, or large enough to power your RV - there's a wide range of options out there.

Factors that are more important than solar panel size

There are many factors that you should consider before the size of your solar panels, like solar panel efficiency and solar panel warranties. 

Solar panel efficiency

Solar panel efficiency is the percentage of light that strikes the surface of a panel that is converted into usable electricity. Modern solar panels have efficiencies that range from around 17% up to 22.8% in some premium models.

Highly efficient panels take up less space, which will allow you to fit more panels on your roof.

Solar panel warranties

There are two types of warranties that cover solar panels.

The first is the product warranty. This is the period during which you can ask the manufacturer to replace the solar panel should any problem arise. Nowadays, a product warranty of 12 years is standard, but more brands are starting to offer product warranties of 25 years.

The second type of warranty is a performance guarantee. Most mainstream panels have a 25-year production warranty, guaranteeing the panel will produce a certain level of output at every stage of the panel’s life. From the date your panels are installed up until the 25-year mark, the minimum guaranteed output of your panels will gradually decrease.

You can expect an output of close to 100% for year one, gradually down to between 80 and 92 percent for year 25. This loss in output is technically known as solar panel degradation. Some solar panel manufacturers, such as Canadian Solar, even offer a 30-year performance warranty on certain panel models.

Find out if solar panels are worth it for your home

How to find the best solar panel size

The easiest way for homeowners to figure out the best solar panel size for their needs is to work with a dedicated solar installer. Solar installers will size your system based on your energy needs, coupled with your available roof space and the sunlight in your area. They can recommend a system size that can fit on your roof and reduce or eliminate your electric bill. 

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I am matching panels and invert to maximize utilization. please help
I am limited to 25 panel of similar size.

the decision is between Lumina1 SS9-72HD 535 panel vs Philadelphia 144-550w panel.
the inverter of interest is the SRNE-HESP thanks to @42OhmsPA guidance.

the specs are below with my newbie calculation (adjusting for low temp of -3C for my location.)
Please comment on:
1/ 72 cells vs 144 cells panel type in general and which panels would you choose .
2/ temperature calculation
3/ string and system sizing
4/ anything helpful.

thank you

Panels comparison
STDLumina I
SS8-72HD -535w bifacialPhiladelphia M144

550W-bifacialMax Power Pmax535 w 550 wVoc49..25Vmp41..19Short-circuit Isc13..69Max power current Imp12..05module eff20.71%21.3% NMOTMax Power Pmax404wVoc46.30Vmp38.80Short-circuit Isc11.05Max power current Imp10.43Open vol temp coef Voc-0.265%/C-0.22Power temp coef PMP-0.334-0.35NOCT+/-2

SRNE inverter model HESPu

Number of MPPT2​Max PV inputw/w​Max. input current25Amp + 25Amp​Max Voc550Vdc + 550 Vdc​MPPT vol range125-450Vdc/125-450Vdc​
Coldest temp in my area is -3C.
Low temp adjusted calculations and string sizing

Lumina I
SS8-72HD -535w bifacialPhiladelphia M144
550W-bifaciallow temperature adjusted56.11 v per panel55.42 v each2 strings of 6 per MPPT
336.6 V – 27.56Amp amp over limit of 25332 V -27.4 Amp
amp over limit of 252 strings of 6 =12 modules in each MPPT12x535w = w12x550w = wtotal system: 24 modules in 4 strings W W I don't think you can go wrong with either panel choice.

Personally I would go with the Philadelphia solar since they are slightly more efficient being 144 cell.

6S2P per MPPT is the best option for 24 panels, you've already figured that out.

I wouldn't have any concerns being slightly over the "max" current input. In ideal conditions you will lose out on a little bit of power but it will be negligible in the grand scheme of things.
My MPPTs are W 22A limit.
Here's what happens you hit the max.

...nothing, the MPPT just stops taking power in.


Your math looks good to me, nice well laid out post too.


I'm sure some others will chime in soon enough. I haven't double-checked the math, but 6s2p could be 6s oriented SE or SSE and the other 6s oriented SW or SSW. Then likely no clipping at all.
It will reduce depth of cycle of battery, charges earlier in the day an keeps charged later.

Looks like from your figures, only standard test conditions might exceed 25A. NMOT does not.
is 25A max operating current, or max allowed short-circuit current? The data sheets I've found are for different model and don't clarify that.

On the other hand, if you have NEM 2.0 reservation with PG&E, then you may want to favor late afternoon production. But maybe not, since although price is 1.5x or 2x as high, production is reduced when not due South.

Panels are cheap. Batteries are more expensive, unless DIY. So I recommend over-paneling.

25 panels fit? So roof mount? I guess you will have 24 panels as 2x 6s2p.
I see the pallet of 31 is same price as 26 individual panels (It is recommended to buy a couple extra in case broken in shipping or installation.)
Not knowing how they differ, it would seem $ less is the way to go. About 3% less STC wattage rating, only 1.5% less CEC PTC rating.

If you do have 2 strings of different orientations, you may be able to parallel another 6 if you can fit them somewhere. Like vertical on a fence?

I haven't double-checked the math, but 6s2p could be 6s oriented SE or SSE and the other 6s oriented SW or SSW. Then likely no clipping at all.
It will reduce depth of cycle of battery, charges earlier in the day an keeps charged later.

Looks like from your figures, only standard test conditions might exceed 25A. NMOT does not.
is 25A max operating current, or max allowed short-circuit current? The data sheets I've found are for different model and don't clarify that.

On the other hand, if you have NEM 2.0 reservation with PG&E, then you may want to favor late afternoon production. But maybe not, since although price is 1.5x or 2x as high, production is reduced when not due South.

Panels are cheap. Batteries are more expensive, unless DIY. So I recommend over-paneling.

25 panels fit? So roof mount? I guess you will have 24 panels as 2x 6s2p.
I see the pallet of 31 is same price as 26 individual panels (It is recommended to buy a couple extra in case broken in shipping or installation.)
Not knowing how they differ, it would seem $ less is the way to go. About 3% less STC wattage rating, only 1.5% less CEC PTC rating.

If you do have 2 strings of different orientations, you may be able to parallel another 6 if you can fit them somewhere. Like vertical on a fence?

@Hedges
thank you for pointing out the the lumina is 144 cells.
Thankyou both Hedges and 42OhmsPA for commenting. I agree that 144 cell (or half cut in general) is a good safe choice. I think it's more likely to hedge against a newbie design error, than it is to confuse an MPPT. Depending on when your main power usage is, it may not really matter (IE if you mostly want to chop summer loads back, you're probably massively overproducing anyway so the half cut giving you an extra 30 min of low angle production, and 0.5% efficiency boost, isn't that much $)

I would recommend holding off on buying the inverter until you have the full inverter + battery approvals (from AHJ and POCO) in hand. With potential tariff changes, there's an argument to buy a more expensive, known quantity for California approval, inverter and battery sooner.

I found this datasheet and it says 25A max input but NO max ISC. Typo? The Euro 230V one has different specs. I don't know if there's an official way in NEC to scale from max input current to max ISC. I think it is fine but I worry about warranty and plan check




Solar panels IMO are mostly determined by how they fit your roof. They do have a different risk (IE, turned out to have missing certifications; can be really expensive to return. If the solar panel can be found in the interconnection application web app it's probably not that bad of a risk).

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This is the one I am following to see that the 12kpv gets listed, before I start my ESS interconnection application. IT covers the inverter and battery combination

I don't see SRNE on there, so it might just not be approved in this manner, or they delegated approval to a different company & it's showing up as a different name


Alternatively I might just do 18kpv, there's some followup work on my house I dream of doing, which that can help with.