What is actually inside a panel
A solar panel is a set of solar cells wired together. Each cell is a thin wafer of silicon, the same material used to build computer chips and the second most abundant material on Earth after oxygen. When sunlight hits the silicon, its energy transfers to electrons inside the material, giving them enough energy to move. Manufacturers process the wafer differently on its 2 faces so it forms a diode, a structure that only lets current flow in 1 direction, and that structure is what turns the electrons set moving by sunlight into a usable electric current instead of a random drift. About 95% of commercial solar panels sold today are built this way, from monocrystalline or polycrystalline silicon.
A single cell barely makes enough power to matter alone
A single photovoltaic cell is thinner than 4 human hairs stacked together, and it typically produces only about 1 to 2 watts of power on its own, not enough to run anything by itself. Manufacturers wire many cells together into 1 panel, called a module, then wire panels together into an array, the full set a home or a business actually runs on. Every cell makes direct current, electricity that flows in 1 steady direction, but a house and the electric grid both run on alternating current, so an inverter sits between the array and the building to convert 1 into the other before anyone can use the electricity.
The single cell figure is the Department of Energy general figure for 1 typical photovoltaic cell, source 4. The panel figure is from the Qcells Q.TRON panel specification sheet, source 5. This chart compares a single cell to a finished panel, not 1 cell inside that specific panel, which is built from 108 half cut cells wired together, not simple addition of the single cell figure.
Show the numbers
| Single solar cell | 1 to 2 watts |
| Qcells Q.TRON panel | 415 to 440 watts |
Why even a well built cell turns most sunlight away
Physics sets a hard ceiling. The Department of Energy states that the theoretical maximum efficiency for a silicon solar cell is about 32%, no matter how well it is manufactured. 3 things eat into that ceiling before a real panel ever gets built. Bare, untreated silicon reflects more than 30% of the sunlight that hits it, which is why manufacturers add an anti reflective coating and a textured surface, and why a high efficiency cell looks dark blue or black instead of the shiny grey of bare silicon. Heat also costs efficiency, because a hotter cell produces slightly more current but a much larger drop in voltage, so a panel makes less usable power on a hot day even with the same sunlight falling on it. Some electrons also recombine, meaning they lose their extra energy before the cell can capture it as current.
The physics limit and the typical range for commercial silicon panels come from the Department of Energy, source 1. The 22.5% figure is from the Qcells Q.TRON panel specification sheet, source 5.
Show the numbers
| Physics limit | 32 |
| Typical panel low end | 18 |
| Typical panel high end | 22 |
| Qcells panel sold now | 22.5 |
The number that is actually on a panel for sale today
The Department of Energy states that commercial silicon panels available today typically reach 18% to 22% efficiency. The Qcells Q.TRON panel, a residential model built from 108 half cut monocrystalline silicon cells and sold now, is rated at up to 22.5% efficiency in its own specification sheet, putting it at the top of, or just past, that typical range. Its maker also guarantees the panel will still produce at least 90.58% of its rated power after 25 years. Even so, the newest panel a homeowner can buy today still turns most of the sunlight reaching it into heat and reflected light rather than electricity.