  Although late-type dwarfs and giant stars are substantially different, their
flares are thought to originate in similar physical processes and differ only
by a scale factor in the energy levels. We study the validity of this approach.
We search for characteristics of flares on active giants, which might be
statistically different from those on main-sequence stars. We used nearly 4000
flares of 61 giants and 20 stars of other types that were observed with Kepler
in long-cadence mode, which is the only suitable database for this comparative
study. For every flare, we derived the duration and energy and gathered stellar
parameters. Correlations between the flare characteristics and various stellar
parameters were investigated. Strong correlations are found between the flare
duration and the surface gravity, luminosity, and radii of the stars. Scaled
flare shapes appear to be similar on giants and dwarfs with a 30 min cadence.
The logarithmic relation of flare energy and duration is steeper for stars with
lower surface gravity. Observed flares are longer and more energetic on giants
than on dwarfs on average. The generalized linear scaling for the logarithmic
relation of flare energy and duration with a universal theoretical slope of
$\approx$1/3 should slightly be modified by introducing a dependence on surface
gravity.
