Solar Panel Efficiency Explained

What efficiency means

Panel efficiency is the percentage of the daylight hitting a panel that it converts into electricity. Most modern domestic panels sit somewhere in the high teens to low twenties as a percentage.

When it actually matters

Efficiency matters most when roof space is limited. If you can only fit eight panels, higher-efficiency panels generate more from that space. If you have a large unshaded roof, a lower-efficiency panel at a better price may deliver more electricity per pound spent.

What matters more than headline efficiency

• Roof orientation and pitch — south-facing generates most; east/west spreads output across the day.
• Shading — even partial shading can disproportionately reduce output.
• System design — correct sizing and a good inverter.

Judge the estimate, not the spec sheet

The number to compare between quotes is the estimated annual generation (kWh) for your specific roof — not the panel efficiency percentage in isolation.

This article is general information. Costs and savings vary by property, energy use and tariff.