Or you could convert your Number item to one which has a unit of measurement (UoM):
I’ve just tried the second method, and it works very nicely:
items
nTemperature1 is the raw value from the binding, nTemperature2 is the same value, but the Item is now specifically a Temperature number, with an initial unit of °C.
So I guess for your specific situation, you could change your Item definition:
Number:Power Solar_AC_Power "AC Power [%.2f W]" {channel="fronius:powerinverter:mybridge:myinverter:inverterdatachannelpac"}
Then in the sitemap:
Text item=Solar_AC_Power label="Solar Power [%.2f kW]"
Note, however, that if you use the state of Item Solar_AC_Power in a rule you will have to modify the rule to take account of the fact that it now comes with the unit embedded within. Or use a second Item just for displaying on the sitemap…