An intense neutral beam injected into a plasma creates a tail (i.e. non-Maxwellian component) in velocity distribution function of the same species as the one injected with enhancing (or reducing) fusion reactivities from the values for Maxwellian plasmas. In a typical D-3He startup operation with field reversed configuration (FRC), tail effect on reduction in neutral beam injection (NBI) power required for plasma heating is investigated. It is shown that as a result of effective tail control, the required NBI power can be reduced by about 60 % from the value for Maxwellian plasma.