  We analyze the effect of different types of fluctuations in internal electron
energy on the rates of dark and photon counts in straight current-carrying
superconducting nanowires. Dark counts appear due to thermal fluctuations in
statistically independent cells with the effective size of the order of the
coherence length; each count corresponds to an escape from the equilibrium
state through an appropriate saddle point. For photon counts, spectral
broadening of the deterministic cut off in the spectra of the detection
efficiency can be phenomenologically explained by local thermal fluctuations in
the electron energy within cells with the same effective volume as for dark
counts.
