Solar panel efficiency measures the percentage of sunlight a panel converts into electricity. Most residential panels in 2026 operate between 20–23% efficiency under standard test conditions (STC). The higher the efficiency, the more power per square foot — which matters most when roof space is limited.
When you think of solar panel efficiency, you’re most likely thinking about how much sunlight a given panel turns into electricity. While this is certainly an important consideration for customers choosing a new photovoltaic system, it’s far from the only aspect of “efficiency” that goes into a high-performing PV system.