Common Sizes of Solar Panels

3.1 kW | Andover, MA

People often ask us about common sizes of solar panels.  When a person refers to size, we can talk about physical characteristics, number of cells, and power.  In this post, I will be covering solar panels used in grid-tied PV systems since off-grid equipment can be very different.

1. Physical Size

Length and Width – Although length and width varies slightly, most companies are manufacturing solar panels in standard sizes.  The most typical size used for residential installations is 65 inches by 39 inches, while the common size for commercial applications is 77 inches by 39 inches.  The smaller size is a better fit for residential projects to maximize available roof space.  Most commercial projects have hundreds of panels and this is why the slightly larger panel is a more ideal choice.  SunPower is the exception to length and width. Their residential panel is 61 inches by 41 inches, slightly shorter and a little wider than standard panels.

Depth – The depth of solar panels range between 1.4 inches to 1.8 inches, although we are seeing more manufacturers move to a 1.8 inch depth.

Weight – Residential solar panels weigh about 40 pounds while the slightly wider commercial panels weigh closer to 50 pounds.   In Massachusetts, we always do a structural analysis to calculate if a roof can withstand the additional weight of the solar equipment.   The weight of the solar panels may be important in scenarios where reinforcement is needed and there is no access to the framing.

2. Number of Solar Cells

Cells are the electrical device that converts sunlight into electricity.  In order to generate a useful amount of power, cells are connected together in a solar panel.  60 cell modules are the industry standard for residential applications, but slightly larger commercial panels are generally 72 cells.  SunPower, the leader in solar panel efficiency, utilizes 96 cell panels.  Solar installation companies often look at the number of cells when determining compatibility with microinverters.

3. Power Rating, or Wattage

In regards to power, size is typically referred to in DC watts under STC or PTC conditions.  STC, or Standard Test Conditions, is the power rating measured under laboratory conditions. STC is what a solar panel manufacturer uses in their technical specifications of equipment.  Most standard panels are between 23o and 275 watts DC STC, while SunPower manufacturers high-efficiency equipment in the range of 327 to 345 watts.  PTC, or PV USA Test Conditions, is the power rating under more “real world” conditions.  The PTC of a solar panel is typically 10-15% lower than its STC.  For standard panels, the PTC is typically between 195 and 247 watts DC.

Brightstar Solar will help our customers choose solar panels that best fit their preferences, the physical space, and electrical design.  We are a Massachusetts solar installer that works with customers to navigate the installation process, maximize incentives and low-interest financing opportunities, and manage the rebate and permitting paperwork involved.  If you have a business or home in Massachusetts and are interested in solar power, please contact us for a free evaluation.