The Federal Office for Economic Affairs and Export Control (BAFA) in Germany needs the following documents and certificates to add a solar collector to the list of collectors eligible for subsidies:
Solar KEYMARK certificate
Test report as per DIN EN 12975 (the test report is rewritten for OEM collectors)
Proof of annual minimum collector gain of 525 kWh/m² for the "Würzburg location"
Proof of a gross collector area of at least 7.0 m2 for vacuum tubes and vacuum flat plate collectors and 9.0 m2 for flat plate collectors
Proof of buffer storage of at least 50 liters / square meter of gross collector area for vacuum tubes and vacuum flat plate collectors and 40 liters / square meter of gross collector area for flat plate collectors