There have only been two instances where the Death Star fired its Superlaser at full power while targeting a planetary body. The Death Star's first test firing destroyed the remote and uninhabited planet Despayre. The first Death Star was built in orbit around Despayre, making it an ideal choice to test the Superlaser's power as well as destroy the evidence of the Death Star's construction. The second instance was the highly publicized destruction of Alderaan.
The Superlaser's power needs to be recharged between blasts, limiting it to only one planet-destroying beam per day. The output of the Superlaser can however be scaled to fire at smaller targets such as capital ships. The Superlaser can produce a scaled beam at a recharge rate of one per minute.
It takes 168 Imperial gunners to operate the Superlaser. There are 14 gunners manning each tributary laser while the remaining crew operates other systems. The Superlaser can only be fired under direct orders from the station commander or the Emperor himself.