In the next years, household appliance test will focus on EMC, CFC replacement, energy efficiency label and reliability, and international certification.

Based on sustainable development,CO_2 emerges as one of the most likely alternatives to the synthetic fluids in heat pump water heaters.

This paper discusses a simple method which is able to provide the COP and the capacity of a theoretical refrigerating cycle using alternatives as working fluids, by means of some new relative factors such as the reduced difference of the cycle temperature, the reduced suction temperature and subcooling temperature.