Panel Selection
Initial Panel Selection
Preliminary panel selection is primarily used to support your Utility Interconnect Application. If you are going with rooftop solar, choosing a 390-450 watt panel will get you what you need for the application and for your preliminary physical design. These panels come in typical sizes of 39-41" width and 72-81" length. Ground Mount arrays can take advantage of larger bifacial panels. In both cases, once your project is set up by HAREI in OpenSolar, there is a relatively short list of top-rated panels to choose from.
There are many criteria for final panel selection. Often final selection is driven by what is available! Factors to consider beyond availability include:
Aesthetics - do you want black or are aluminum-colored frames OK. For residential applications the premium for black is small. Black is most common for residential installations.
We seek out Tier 1 Solar manufacturers (for financial stability/viability), and panels that have proven to be Top Performers in independent accelerated life testing (for long-term reliability. )
Monofacial or Bi-Facial - there are now panels (bi-facial) that generate electricity from reflected light on the backside. Typically the power ratings are only from power generated on the front side. There is no technical benefit to bi-facial on a pitched roof. You will see them used on flat roofs with a light-colored roofing and, most commonly, on ground mount installations. Other than flat roof and ground mount application, the other reason you might select bi-facial is cost per watt. Most pitched roof intllations are not bi-facial.
Cost - The cost per DC watt can vary widely. HAREI sees occasional opportunities to purchase at less than $.50 per DC watt. Most recently prices have been between $.60 and $1.25 per DC watt.
US made - You may have a bias toward US manufactured vs. non-US. There is also an additional 10% tax credit in the Inflation Reduction Act if you have enough US content. There is a growing number of US manufacturers. Generally, they are substantially more expensive than technically comparable alternatives.
Final Panel Selection
Once the Utility has approved your Interconnect Application, then you need to join a working meeting and discuss the best price/watt of panels and availability. Once you have confirmed availability of panels that meet your criteria, you may have do a quick re-design before ordering materials.
You will also need to check the lead/wire length on the specific panels to ensure they will reach the inverter/optimizer locations on your racking system design. If not, your will need to reconsider which rail you inverters or optimizer and the connecting cable are mounted, or buy or make extensions for the wires coming from the panels.