Final answer:
It is false that most German homes have air conditioning. Modern home design in Germany focuses on energy efficiency through insulation and passive heating, not reliance on air conditioning systems. Efficient operation of cooling appliances is achieved with minimal temperature differences between reservoirs, leading to a better COP.
Step-by-step explanation:
The statement that air conditioning can be found in most homes in Germany is false. German homes tend to be designed with energy efficiency in mind and do not commonly include air conditioning systems. The misconception may stem from the idea of modernity equating to the presence of air conditioning; however, in Germany, and other parts of Europe, modern home design emphasizes insulation, passive solar design, and natural ventilation over mechanical cooling.
In reference to homes that are kept warm without heating systems, this is possible due to superior insulation and design that retains heat within the home. Heat from the sun, human inhabitants, and domestic equipment all contribute to maintaining a warm interior.
Regarding the cost-effectiveness of cooling appliances like refrigerators and air conditioners, they operate most efficiently when the temperature difference between Th (the high temperature reservoir) and Tc (the cold temperature reservoir) is minimal. A small temperature difference leads to a higher coefficient of performance (COP), indicating a more efficient operation.