Solar Panel Efficiency explained
Solar panel efficiency measures how well a panel converts sunlight into electricity. A panel with 20% efficiency converts 20% of the solar energy striking its surface into electrical power — the rest is lost as heat or reflected away.
Efficiency matters most when roof space is limited. A higher-efficiency panel produces more watts per square metre, so you can fit more generating capacity on a smaller roof.
Here's a rough guide to typical efficiency ranges in 2024–2026:
- Standard monocrystalline: 18–22%
- Premium monocrystalline (e.g. SunPower, REC): 22–24%
- Polycrystalline: 15–18%
- Thin-film (e.g. CadTel): 10–13%
In practice, most homeowners should focus on the system output in kWh per year rather than chasing the highest efficiency rating. A slightly less efficient panel from a reliable brand often represents better value. That said, if your roof is small or partially shaded, high-efficiency panels make a meaningful difference.
Panel efficiency also degrades slightly over time — typically around 0.5% per year — so a 20% efficient panel will perform at about 10% reduced efficiency after 20 years.