Due to their high global warming potential (GWP), fluorinated refrigerants are being replaced in many heat pump and refrigeration systems. Especially in small systems such as heat pump tumble dryers (HPTD), the replacement of the globally used working fluid in this application, R134a, appears to be manageable. One established alternative is the use of hydrocarbon refrigerants. Within this research project, new zeotropic refrigerant blends of hydrocarbons are theoretically evaluated as retrofit substitutes for R134a in heat pump tumble dryers. The aim is to use the temperature glide inherent to zeotropic mixtures during phase change to increase the heat transfer efficiency and thus, the COP of the system. A mixture of R290 (propane) and RE170 (dimethyl ether) was selected and experimentally investigated in a commercially available HPTD. To assess the new mixture, parameters relevant to the cycle such as pressure, temperature, compressor power, and the dryer moisture extraction rate are compared to those values achieved using the refrigerant R134a. Retaining the heat exchanger and compressor from the R134a system, the system charge with the new mixture was 40 % lower, while the thermal capacity was equal to or higher than that of the R134a system. The increased temperature level supplied by the mixture reduced the drying time and the energy consumption of the HPTD. The investigation showed that the heat exchanger design needed to be adapted to the temperature glide properties of the mixture in order to realize meaningful heat transfer efficiency gains.