 The more energetic superflares seem to be ruled out by energetic considerations for our sun, which suggest it is not capable of a flare of more than 1034 ergs.A calculation of the free energy in magnetic fields in active regions that could be released as flares gives a lower upper bound of around 3×1032 erg suggesting the most energetic a super flare can be is three times that of the Carrington event.Some stars have a magnetic field 5 times that of the Sun and rotate much faster and these could theoretically have a flare of up to 1034 ergs.