A system and method for evaluating parameters for a refrigeration system having a variable speed compressor is provided. A compressor is connected to a condenser and an evaporator. A condenser sensor and an evaporator sensor are provided. An inverter drive modulates a frequency of electric power delivered to the compressor to modulate a speed of the compressor. A monitor module receives compressor power data and compressor speed data from the inverter drive, determines a measured condenser temperature based on the condenser signal, determines a measured evaporator temperature based on the evaporator signal, calculates a first derived condenser temperature based on the compressor power data and the compressor speed data, calculates a second derived condenser temperature based on the measured evaporator temperature, the compressor power data and the compressor speed data, and compares the measured condenser temperature with the first and second derived condenser temperatures to determine whether any of the measured condenser temperature and the first and second derived condenser temperatures are inaccurate.