7 Things You Need To Know  About Solar Panel Ratings

There are two types of solar panels commonly used for domestic installations - monocrystalline (up to 22%) and polycrystalline (15 to 17%).

Panels are mostly sold by their STC rating in watts (Standard Test Conditions). These are ideal conditions that rarely exist in real life

Irradiance 1000W/m2

Solar Panel STC Rating

Temperature  25 degrees C

NOCT solar panel rating standards are much more realistic - actual wattage output is around 25% less than the normal rating!

Temperature 20 degrees C Insolation 800W/m2 Breeze 1m/sec

Solar Panel tilt angle affects the output. About 45% is good - adjusting by season is better.

Flat isn't disastrous but 90 degrees is a big no-no!

Solar panel direction has an effect on output

Due South (in the Northern hemisphere) is optimum. South-East and South-West are OK, but never North!

Auto-tracking (following the sun across the sky) increases energy output

Single-axis tracking gives about 40% gain Dual-axis tracking can give up to 60% gain.

Excess heat affects solar panel output

A solar cell output capacity reduces by 0.5W for every degree rise in temperature (centigrade)

Clean those panels!

Regular cleaning can increase electricity generation by 10% to 25%

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