How accurate are SolarFarmer energy predictions?

SolarFarmer accuracy is very important. SolarFarmer is validated against a growing set of operational sites by comparing output and analyzing error distributions for systematic biases. The summary results in the validation section of the documentation [1] are updated with every release. The average annual mean bias error is less than 0.2% for all five sites in the study as of January, 2021, when version was released.

A detailed analysis of the validation study was presented in “Validation of the Solarfarmer Software with Operational Data” by Anja Neubert at the 2020 EU PVSEC [2]. The proceedings are open & free to download. Most of the systems in the study were fixed-tilt monofacial modules on flat terrain, but there was one bifacial tracker system on rolling terrain. The sites in the study were all located either in the USA or the UK.

[1] Results summary | SolarFarmer Documentation
[2] EU PVSEC Proceedings - Validation of the Solarfarmer Software with Operational Data