An excavator having: an upper structure that pivots about a pivot axis relative to an undercarriage, and a hydraulic system (10; 210; 510) comprising: an accumulator (34; 234; 534); and a hydraulic transformer (26; 26a; 26b; 26c) including first and second variable displacement pump/motor units (100, 102; 200, 202; 500, 502) connected to a rotatable shaft (36; 104; 236; 536), the rotatable shaft (36; 236; 536) adapted for connection to an external working load (38; 238; 538), the first variable displacement pump/motor unit (100; 200; 500) including a first side that fluidly connects to a hydraulic pump (12; 212; 512) and a second side that fluidly connects to a tank (18; 218; 518), the second variable displacement pump/motor unit (102; 202; 502) including a first side that fluidly connects to the accumulator (34; 234; 534) and a second side that fluidly connects with the tank (18; 218; 518); characterized in that the rotatable shaft includes a first portion that connects the first and second variable displacement pump/motor units (100, 102) and further includes a second portion that forms an output shaft that is adapted for mechanical connection to the upper structure of the excavator, the rotatable shaft (36; 236; 536) being used to pivot the upper structure about the pivot axis, and wherein the hydraulic transformer is part of a first load circuit (22; 222; 522) powered by the hydraulic pump (12; 212; 512), wherein the hydraulic system includes a second load circuit (24; 224; 524) powered by the hydraulic pump (12; 212; 512), wherein the hydraulic transformer can transfer energy corresponding to a deceleration of the external working load (38; 238; 538) to the accumulator (34; 234; 534), and wherein the hydraulic transformer (26; 26a; 26b; 26c) can also transfer energy corresponding to a deceleration of the external working load to the second load circuit (24; 224; 524). an upper structure that pivots about a pivot axis relative to an undercarriage, and a hydraulic system (10; 210; 510) comprising: an accumulator (34; 234; 534); and a hydraulic transformer (26; 26a; 26b; 26c) including first and second variable displacement pump/motor units (100, 102; 200, 202; 500, 502) connected to a rotatable shaft (36; 104; 236; 536), the rotatable shaft (36; 236; 536) adapted for connection to an external working load (38; 238; 538), the first variable displacement pump/motor unit (100; 200; 500) including a first side that fluidly connects to a hydraulic pump (12; 212; 512) and a second side that fluidly connects to a tank (18; 218; 518), the second variable displacement pump/motor unit (102; 202; 502) including a first side that fluidly connects to the accumulator (34; 234; 534) and a second side that fluidly connects with the tank (18; 218; 518); an accumulator (34; 234; 534); and a hydraulic transformer (26; 26a; 26b; 26c) including first and second variable displacement pump/motor units (100, 102; 200, 202; 500, 502) connected to a rotatable shaft (36; 104; 236; 536), the rotatable shaft (36; 236; 536) adapted for connection to an external working load (38; 238; 538), the first variable displacement pump/motor unit (100; 200; 500) including a first side that fluidly connects to a hydraulic pump (12; 212; 512) and a second side that fluidly connects to a tank (18; 218; 518), the second variable displacement pump/motor unit (102; 202; 502) including a first side that fluidly connects to the accumulator (34; 234; 534) and a second side that fluidly connects with the tank (18; 218; 518); characterized in that the rotatable shaft includes a first portion that connects the first and second variable displacement pump/motor units (100, 102) and further includes a second portion that forms an output shaft that is adapted for mechanical connection to the upper structure of the excavator, the rotatable shaft (36; 236; 536) being used to pivot the upper structure about the pivot axis, and wherein the hydraulic transformer is part of a first load circuit (22; 222; 522) powered by the hydraulic pump (12; 212; 512), wherein the hydraulic system includes a second load circuit (24; 224; 524) powered by the hydraulic pump (12; 212; 512), wherein the hydraulic transformer can transfer energy corresponding to a deceleration of the external working load (38; 238; 538) to the accumulator (34; 234; 534), and wherein the hydraulic transformer (26; 26a; 26b; 26c) can also transfer energy corresponding to a deceleration of the external working load to the second load circuit (24; 224; 524).