diff --git a/fhem/CHANGED b/fhem/CHANGED
index d127fc9cc..04619d63a 100644
--- a/fhem/CHANGED
+++ b/fhem/CHANGED
@@ -1,5 +1,6 @@
 # Add changes at the top of the list. Keep it in ASCII, and 80-char wide.
 # Do not insert empty lines here, update check depends on it.
+ - change:  59_WUup: use UConv to calculate solarradiation from lux to W/m²
  - change:  74_AMADDevice: add logreport is attribut fhemServerIP not set
  - change:  93_DbRep: better logfile messages in some cases of index operation
  - feature: 44_TEK603: new attribute "disable" 
diff --git a/fhem/FHEM/59_WUup.pm b/fhem/FHEM/59_WUup.pm
index 728ced14b..fc4031379 100644
--- a/fhem/FHEM/59_WUup.pm
+++ b/fhem/FHEM/59_WUup.pm
@@ -33,7 +33,7 @@ use HttpUtils;
 use UConv;
 use FHEM::Meta;
 
-my $version = "0.9.12";
+my $version = "0.9.13";
 
 # Declare functions
 sub WUup_Initialize($);
@@ -280,7 +280,7 @@ sub WUup_send($) {
 
             if ( $attr{$name}{unit_solarradiation} eq "lux" ) {
                 Log3 $name, 5, "WUup ($name) - solarradiation unit is lux";
-                $value = ( $value / 126.7 );
+                $value = UConv::lux2wpsm( $value, $rnd );
             }
             else {
                 Log3 $name, 5, "WUup ($name) - solarradiation unit is W/m²";
@@ -378,6 +378,7 @@ sub WUup_receive($) {
 # 2019-07-04 replaced link to API documentation
 # 2019-07-05 add Meta support
 # 2019-07-09 add WIKI to Meta data
+# 2020-03-12 use UConv to calculate solarradiation from lux to W/m²
 #
 ################################################################################