When you check the specifications of solar panels they have listed power tolerances + or -. For example + 2 or -3, would someone explain what this is refering too? Thanks
Steve
Comments
The specified range within which a solar panel will either overperform or underperform its rated power Pm at STC.
Power tolerance can vary greatly, from as much as +10% to -10%. A 220 watt panel with ±10% rated power tolerance may produce between 198 Watts and 242 Watts. To ensure expected power output, look for panels with a small negative (or positive only) power tolerance.
Most solar panels work in the range of ±3%.
But there are some solar panels (eg.1) that refer to their power tolerance as -0%, +3%, which I believe a good reason of reliability and a strong marketing.
Comments
The specified range within which a solar panel will either overperform or underperform its rated power Pm at STC.
Power tolerance can vary greatly, from as much as +10% to -10%. A 220 watt panel with ±10% rated power tolerance may produce between 198 Watts and 242 Watts. To ensure expected power output, look for panels with a small negative (or positive only) power tolerance.
Most solar panels work in the range of ±3%.
But there are some solar panels (eg.1) that refer to their power tolerance as -0%, +3%, which I believe a good reason of reliability and a strong marketing.
Please take a look at the Webinar "PV Module Power Rating" (.pdf presentation) from solarabc.org. It explains the calculation method of power output tolerance.