A waste-watermill (12, 12 I, 12 II) for generating electrical energy from a flow of waste water (14, 14 I, 14 II) running through an underground waste-water conduit (50, 50 I, 50 II), said flow of waste water (14, 14 I, 14 II) defining a free surface (16, 16 I, 16 II) and a flow direction inside said waste water conduit, said waste-watermill (12, 12 I, 12 II) comprising: a water wheel (22, 22 I, 22 II) for being driven by said flow of waste water (14, 14 I, 14 II) in an undershot configuration, an axle (28, 28 I, 28 II) for defining a rotational axis for said water wheel (22, 22 I, 22 II), said rotational axis being positioned above said free surface (16, 16 I, 16 II) and oriented transverse to said flow direction in said undershot configuration, a wheel support (26, 26 I, 26 II) for rotationally supporting said water wheel (22, 22 I, 22 II) in said undershot configuration and in a stationary position relative to said underground waste-water conduit (50, 50 I, 50 II), said wheel support (26, 26 I, 26 II) is adapted for positioning said water wheel (22, 22 I, 22 II) such that said rotational axis is located below the top of said waste-water conduit (48, 48 I, 48 II) and closer to the top of said waste-water conduit (48, 48 I, 48 II) than to the bottom of said waste-water conduit (50, 50 I, 50 II), and an electric generator (34, 34 I, 34 II) operatively connected with said water wheel (22, 22 I, 22 II) and said axle (28, 28 I, 28 II) for being driven by said water wheel (22, 22 I, 22 II) to produce electrical energy, wherein said water wheel (22, 22 I, 22 II) comprises a paddle (52, 52 I, 52 II, 52 III, 68, 68 I, 68 II, 68 III) for being pushed by said flow of waste water (14, 14 I, 14 II) to drive said water wheel (22, 22 I, 22"), said paddle (52, 52 I, 52 II, 52 III, 68, 68 I, 68 II, 68 III) extends in a radial direction relative to said rotational axis, and said water wheel (22, 22 I, 22 II) comprises a paddle support (54, 54 I, 54 II) interconnecting said paddle (52, 52 I, 52 II, 52 III, 68, 68 I, 68 II, 68 III) and said axle (28, 28 I, 28 II) for supporting said paddle (52, 52 I, 52 II, 52 III, 68, 68 I, 68 II, 68 III), said paddle (52, 52 I, 52 II, 52 III, 68, 68 I, 68 II, 68 III) defines a paddle profile when viewed in a direction perpendicular to said radial direction and said rotation axis, and said paddle profile has a curved distal edge (70, 70 I, 70 II, 70 III) corresponding to the bottom portion of the cross-sectional cut of said wastewater conduit (50, 50 I, 50 II). a water wheel (22, 22 I, 22 II) for being driven by said flow of waste water (14, 14 I, 14 II) in an undershot configuration, an axle (28, 28 I, 28 II) for defining a rotational axis for said water wheel (22, 22 I, 22 II), said rotational axis being positioned above said free surface (16, 16 I, 16 II) and oriented transverse to said flow direction in said undershot configuration, a wheel support (26, 26 I, 26 II) for rotationally supporting said water wheel (22, 22 I, 22 II) in said undershot configuration and in a stationary position relative to said underground waste-water conduit (50, 50 I, 50 II), said wheel support (26, 26 I, 26 II) is adapted for positioning said water wheel (22, 22 I, 22 II) such that said rotational axis is located below the top of said waste-water conduit (48, 48 I, 48 II) and closer to the top of said waste-water conduit (48, 48 I, 48 II) than to the bottom of said waste-water conduit (50, 50 I, 50 II), and an electric generator (34, 34 I, 34 II) operatively connected with said water wheel (22, 22 I, 22 II) and said axle (28, 28 I, 28 II) for being driven by said water wheel (22, 22 I, 22 II) to produce electrical energy, wherein said water wheel (22, 22 I, 22 II) comprises a paddle (52, 52 I, 52 II, 52 III, 68, 68 I, 68 II, 68 III) for being pushed by said flow of waste water (14, 14 I, 14 II) to drive said water wheel (22, 22 I, 22"), said paddle (52, 52 I, 52 II, 52 III, 68, 68 I, 68 II, 68 III) extends in a radial direction relative to said rotational axis, and said water wheel (22, 22 I, 22 II) comprises a paddle support (54, 54 I, 54 II) interconnecting said paddle (52, 52 I, 52 II, 52 III, 68, 68 I, 68 II, 68 III) and said axle (28, 28 I, 28 II) for supporting said paddle (52, 52 I, 52 II, 52 III, 68, 68 I, 68 II, 68 III), said paddle (52, 52 I, 52 II, 52 III, 68, 68 I, 68 II, 68 III) defines a paddle profile when viewed in a direction perpendicular to said radial direction and said rotation axis, and said paddle profile has a curved distal edge (70, 70 I, 70 II, 70 III) corresponding to the bottom portion of the cross-sectional cut of said wastewater conduit (50, 50 I, 50 II).