Energy recovery experiments have been conducted for the first time with a negative ion based neutral beam injector. A new type of energy recovery system was utilized, which: (i) separates electrostatically the neutrals and charged components of the beam at the exit of the neutralizer; (ii) decelerates the residual unneutralized negative ions; (iii) prevents secondary emission of electrons from the negative ion collector by means of electrostatic trapping. With 102 keV, 1.2 A D−beams, the residual negative ions have been decelerated with high efficiency down to 8 keV. By taking into account the power consumption of the electrostatic deflector, the recovery efficiency of the residual negative ion beam power was as good as 81%, at a background gas operating pressure around 10−3Pa.