Actually available household cooling appliances in the highest efficiency class may consume less then 10W average electrical power. To achieve such power consumptions special challenges for the cooling system had to overcome. The related cooling system design has to consider several effects, which arise from the corresponding low cooling capacity demand, start/stop cycles and additional power consumptions by control accessories. The lecture provides symptomatic aspects of cooling technology, which have not been fully considered in the past or had only a negligible impact on electrical energy consumption. Those aspects are presented as qualitative descriptions of the phenomena, not as definite data or solutions. Discussed are Compressor related topics, like Efficiency deviations to the rating point related to operation conditions and startup/run time, impact of refrigerant/oil solubility in the reservoir, oil discharge, electronic losses. Refrigerant related topics, like Flow regime in heat exchangers, oil transport, impact of refrigerant location during startup/run time and stopping period. Heat Exchanger related topics, like Fan power, material heat capacity, dynamic behavior, flexible operation demand, tube sizing/pressure drop, capillary design. Some items can be discussed as evolution of key performance data during the last years, like COP of compressors at specific operation points or power consumption for electronic controls.