Electric machines with concentrated winding and single tooth design provide a cost effective way to use flat wires. Hereby high filling factors can be achieved, but due to geometric constraints and the influence of current displacements there remains unused space inside the slot. This space can be used for water cooling channels. As a result of the small thermal resistance between winding and cooling fluid this leads to an outstanding cooling performance. Compared to round wires efficiency is improved in wide parts of the operating area. The absence of the cooling jacket leads to comparable production costs but an even more compact machine design. Technological aspects are discussed and a particular high-power-density interior permanent magnet synchronous machine (IPMSM) with water jacket cooling and round wires is compared to a flat wire wound, slot cooled motor by the use of FEM and CFD simulations and measurements on single tooth specimen.