Frequently Asked Question

How much energy will I save by increasing the setting of my air conditioner's thermostat by one degree?

Because conditions vary, there is no precise answer to this question. The electricity consumed by an air conditioner varies depending on a variety of factors. Generally, you can expect to lower your energy consumption by about 15% with this change. A rough calculation is as follows.

The amount of heat transfer is proportional to the differential between the interior and exterior temperatures. Setting the thermostat at 27ºC when the outside air temperature is 35ºC (the standard design condition for air conditioners) results in a temperature differential of 8ºC. Setting the thermostat to 28ºC results in a differential of 7ºC. A simple calculation shows the amount of incoming heat is 7/8 - in other words, 0.875 - indicating that the air conditioner needs to remove 12.5% less heat.

As the temperature differential decreases, the air conditioner is moving heat between two locations that have less difference in temperature; therefore, a smaller amount of work is required to move the same amount of heat. This effect can be calculated at about 3% per 1ºC.

Therefore, considering these two effects, increasing the setting by 1ºC will reduce power consumption by about 15%. Setting the thermostat at 28ºC saves about 60% compared to a thermostat setting of 24ºC.

In practice, however, other factors come into play, such as the effect of radiant heat, heat from office equipment in the room, and the heat and humidity given off by people in the room. In addition, air conditioners are often used when the outside temperature is lower than that assumed by the designers. Because of these and other factors, the above rough calculation may not reflect your actual situation. However, increasing the setting by only 1ºC clearly leads to substantial energy savings.