Which of the following can affect the efficiency of a heating system?

Each of the factors mentioned plays a significant role in determining the efficiency of a heating system.

Insulation quality affects how well a building retains heat. Poor insulation can lead to significant heat loss, causing the heating system to work harder to maintain the desired temperature. This increased workload not only decreases efficiency but can also lead to higher energy bills and increased wear on the system.

The age of the heating system is also crucial. Older systems tend to be less efficient than newer models, which often incorporate advanced technologies and design improvements. As systems age, components can wear out or become less effective, leading to decreased performance and higher energy consumption.

Thermostat settings directly influence how the heating system operates. If the thermostat is set too high, the system will run longer and use more energy than necessary. Conversely, setting the thermostat appropriately can enhance efficiency by ensuring that the heating system only operates as needed.

Considering these factors, it becomes clear that all of them collectively contribute to the efficiency of a heating system, justifying the selection of the comprehensive answer.