In warm climates, air conditioning can account for a significant share of household electricity use. A simple ceiling fan consumes only a fraction of the power, yet its ability to create a perceived cooling effect allows residents to raise their thermostats. This calculator helps quantify the financial benefit of that strategy. By entering the air conditioner's power draw and daily runtime, the amount by which you can raise the thermostat thanks to the fan, the fan's own energy use, and your electricity rate, you receive an estimate of daily cost savings.
The underlying principle is that most air conditioners run less often when the thermostat is set higher. Industry studies suggest that each degree Fahrenheit of setback reduces cooling energy use by roughly three percent. With a two-degree increase, for example, you could save about six percent. The calculator multiplies your baseline daily cooling energy by this percentage, subtracts the fan's consumption, and converts the result to monetary savings using your electricity rate.
First, the model determines the baseline daily cooling cost without a fan. If your air conditioner draws 3.5 kW and runs for eight hours a day, it uses 28 kWh. At a rate of $0.15 per kWh, that costs $4.20. Raising the thermostat by two degrees would save approximately 6% of that energy, or 1.68 kWh, equivalent to $0.25. Running a 50 W ceiling fan for the same eight hours consumes 0.4 kWh, costing $0.06. The net daily savings is therefore $0.19.
The calculation is summarized in the following MathML expression:
where is savings in dollars per day, is the electricity rate, and are air conditioner power and runtime, is the thermostat increase in degrees Fahrenheit, and and are fan power and runtime. The constant 0.03 represents the three percent savings per degree.
The table below shows expected savings at various thermostat offsets using the default inputs. As you experiment with your own numbers, the table updates to illustrate how larger offsets yield more significant savings.
| Offset (°F) | Net Daily Savings ($) |
|---|
Beyond cost, ceiling fans can improve comfort by mixing air, reducing hot spots near ceilings, and creating a gentle breeze. They also have limitations. Fans cool people, not rooms, so the savings occur only when the room is occupied. Leaving fans running in empty rooms wastes energy. The rule of thumb that each degree saves three percent is an average; older or poorly insulated homes may experience different savings. Additionally, some people may not tolerate higher thermostat settings, especially during extreme heat or humidity.
Use this tool as part of a broader strategy to manage cooling costs. Combine it with weatherization, shade, and smart thermostats for greater benefits. To explore related energy trade-offs, visit the Heated Blanket vs Space Heater Cost Calculator and the Wireless Charging Energy Loss Calculator, which both analyze how comfort and convenience intersect with power consumption.
As a worked example, imagine a household in a humid southern state. Their central air conditioner uses 4 kW and runs nine hours per day during peak summer. Electricity costs $0.12 per kWh. By installing a ceiling fan in the living room and raising the thermostat three degrees, they reduce AC energy by about 10.8 kWh per day, saving $1.30. The fan draws 60 W for ten hours, consuming 0.6 kWh and costing $0.07. The net savings is $1.23 per day, or about $37 per month during peak season. Over an entire summer, the fan quickly pays for itself.
Limitations of this calculator include not modeling humidity effects or variations in AC efficiency. It also assumes the thermostat increase equally reduces runtime, which may not hold if your home has uneven insulation or if occupants engage in frequent door opening. Nevertheless, the tool provides a useful baseline for evaluating whether running fans makes economic sense in your situation.
Thermal comfort is influenced not only by air temperature but also by humidity, clothing, and air speed. Ceiling fans increase air speed, which enhances evaporative cooling on the skin. The calculator does not simulate these physiological effects; it assumes that a given temperature offset is tolerable thanks to the fan. In reality, some individuals may perceive comfort differently, and local weather conditions play a huge role.
From an engineering standpoint, the 3% savings per degree is an average derived from many studies of residential structures. Homes with superior insulation, reflective roofing, or high-efficiency air conditioners may achieve greater savings, while drafty or sun-exposed homes may see less. Advanced users could modify the percentage in the source code to reflect audit data for their specific building.
Future versions of this tool might integrate seasonal energy efficiency ratios (SEER) for different air conditioners or allow separate inputs for occupied and unoccupied periods. Such enhancements could refine accuracy but would also complicate the simple interface that makes this calculator approachable.