From the ground, it can be a bit difficult to judge the size of a solar panel up on a rooftop. Or to tell if all solar panels are the same size. Technology, design and suitability have all played a role in determining the size of solar panels.

The two main types are residential and commercial solar panels. And not surprisingly, commercial panels are longer and heavier than residential ones. But not by much.

Usually when we think about commercial versus residential products, the former is built to more rigorous standards, higher in quality and much more expensive. The truth with commercial and residential solar panels is that both are constructed using identical technologies, with the exact same qualities, and performance specifications.

Likely the most surprising fact is that commercial panels tend to cost less. More about that later.

Residential solar panels can vary in size with widths of 39 to 41 inches, lengths of 65 to 72 inches, thickness of 1.2 to 1.6 inches and weight of 40 to 45 lbs. Higher efficiency panels of >20% are typically made of 60 to 66 monocrystalline (single silicon crystal) photovoltaic cells, which are then half-cut. The resulting 120 to 132 half-cut cells have less connection losses, allow a closer fit and perform better than full cells when a panel is partially shadowed.

The largest residential panels can provide the lowest manufacturing cost per watt of output and making them the best choice when there is plenty of unobstructed south roof exposure to meet solar generation requirements. Less available south exposure or complex roof geometries may favor smaller panels to maximize the watts which can be installed within a given space.

Commercial solar panels usually have 72 monocrystalline cells resulting in 144 half-cut cells, similar in width and thickness to residential panels, but with a length of 78 inches and weight up to 50 lbs. The result is even a further reduction in manufacturing cost per watt, less racking required per watt and lower installation labor cost, as each panel can still be handled by one installer. Commercial solar project economies of scale reduce the cost per watt even more with savings in marketing, design and procurement.

There can be an opportunity to use commercial size panels on a residential project where even more ample prospective roof space exists and the solar contractor can competitively procure commercial panels. Always a good option to look at when the opportunity presents itself.

Future developments are unlikely to change the dimensions of either residential or commercial panels. Instead, the focus will remain on increasing the efficiency and hence the power rating of similar-sized panels through continual refinements in design and materials, with the objective of driving the resulting cost per watt lower.

So the next time you look up at a rooftop and wonder about the size of those panels, you’ll be a bit more informed.