Final answer:
An appliance with efficiency lower than 85% could be considered as having poor energy efficiency, leading to increased energy consumption and costs. This efficiency is measured by the appliance's ability to convert electrical energy into useful output. In refrigeration, it is quantified as the coefficient of performance (COP), which is influenced by temperature differences in the cooling process.
Step-by-step explanation:
If an appliance is less than 85% efficient and described as non-positive, it could be considered as having a poor energy efficiency. Efficiency in this context refers to the ratio of useful energy output to the electrical energy consumed. When an appliance operates at less than ideal efficiency, it consumes more power than is necessary for performing its function, leading to higher energy costs. For instance, upgrading from an older appliance that uses 2.4 kWh/day to a newer, more efficient model that uses 1.8 kWh/day could result in significant energy savings over time.
In the realm of refrigeration, the coefficient of performance (COP) is used to measure efficiency. For example, an ideal refrigerator that cools an environment at -20.0°C with heat transfer to another environment at 50.0°C has a certain COP based on the temperatures involved. Similarly, a hypothetical refrigerator designed to make liquid nitrogen at -200°C with heat transfer to the environment at 35.0°C will have a best possible COP dictated by those temperatures. However, these efficiency measures do not exceed 100% in reality, due to the law of conservation of energy. Using more efficient devices can play a crucial role in energy conservation and cost reduction.