This paper presents the simulation-based development of a novel knitted design of textile heating structures based on dedicated serial-parallel circuits for heating (DSPCh) using silver-plated yarns processed via knitting technology. The DSPCh approach features dedicated and spatially bounded sub-circuits, ensuring even heat distribution and resilience against circuit failures in smart textiles with heating functionality. The study finds that the conductor arrangement and knitting pattern significantly affect the heating performance. DSPCh structures achieve even more heat distribution than serial and parallel circuit designs. Due to its binding, the developed basic pattern based on the right–left knit is less electrically conductive than that based on the right–right knit. Results show that DSPCh structures exhibit a favorable heat level and uniform heat distribution suitable for wearable textiles close to the body. The comparison with other circuit designs demonstrates higher temperatures of maximum 132°C and temperature differences up to 100 K, making DSPCh structures suitable for functional underwear. In addition, the experiments reveal that the heating performance is minimally degraded after standard machine-washing and care protocols. The investigations demonstrate that the DSPCh structures are suitable for actively heatable functional underwear, and simulation tools can aid in predicting temperatures and heat distribution for various textile designs.