  Basing on experiments at SLAC, MAMI, CERN, and on Monte Carlo simulations, we
assess the physical limits on efficiency and reachable angles of electron
deflection in bent crystals in the energy range from sub-GeV to sub-TeV. We
find that applications of electron channeling for beam deflection are possible,
limited by maximal deflection angle of 2-3 mrad at sub-GeV, 1-2 mrad at
multi-GeV, and 0.5-1 mrad at sub-TeV energy. This opens opportunities for
crystal-assisted electron beam extraction from accelerator rings.
