When reviewing different solar proposals, it is important to look closely at the type of solar module being used in the design. There are a few different sizes used by installers, and they will have different capacities, different looks, and varying efficiencies. When looking at the costs associated with each type of installation, just know that you are not usually comparing apples to apples directly.
Historically, when solar cell manufacturers came out with higher-efficiency cells, they assembled these new cells in a 60-cell module first. The modules are 6 cells wide and 10 cells long, producing a full panel that is approximately 39 inches wide and 66 inches tall. These smaller modules can be installed in more confined spaces to maximize energy production. Combine that with improved efficiencies, and you can put more on your roof while still getting the production you desire.
The second standard-sized module is a 72-cell panel. These modules are 6 cells wide and 12 cells long, producing a full panel that is approximately 39 inches wide and 78 inches tall. These taller modules cannot fit confined spaces well, so they are not ideal for residential rooftop use. You more regularly see these modules in commercial applications or ground-mount arrays where there are little or no space restraints. The 72-cell panels are typically using mass-produced cells which tend to have a lower efficiency when compared to what is being used in the residential market. While it does lead to a lower cost, you will get what you pay for in quality, longevity, and efficiency.
Since we tend to nerd out about this stuff here at Rectify, you can consider the following math if it helps you put the sizing in perspective:
The capacity of a 60-cell module: 250W – 365W
The capacity of a 72-cell module: 355W – 395W
Think about it this way:
A 330W 72-cell solar panel is the same efficiency as a 275W 60-cell panel:
330W/72 cells = 4.58 watts/cell
4.58W X 60 cells = 275W solar panel
A 330W 60-cell solar panel is the same efficiency as a 395W 72-cell panel:
330W/60 cells = 5.5 watts/cell
5.5W X 72 cells = 395W solar panel
The important thing to think about if you are looking into installing solar panels for your home or property is to understand exactly what is being proposed in the design. Often, you are not comparing apples to apples from one company to another. Just because you see that larger number incapacity does not necessarily mean that you are getting a “better” panel. Take a close look, ask specific questions to your energy advisor, and make sure you understand the pros/cons of each type of panel before making the decision to move forward on a project.