The cost of air heating for a day is affected by a variety of factors, including house size, insulation performance, outdoor temperature, equipment power, energy efficiency ratio, electricity price, usage time, and indoor temperature setting. Therefore, it is difficult to give a fixed number, but we can estimate based on the general situation.

Taking a 100 to 120 square meter house as an example, if the equipment efficiency is the market average and the local electricity price is 0.5 yuan per kilowatt-hour at the average outdoor temperature in winter, we can make the following estimates:

1. Electricity cost estimation

1. Equipment power: For a 100 square meter home, an air heating system with a power of between 3.8 kW and 4.3 kW is usually selected. To simplify the calculation, let's assume a device power of 4 kilowatts.

2. Power Consumption: When the system is operating at maximum power, it consumes 4 kWh per hour. However, since the air energy heating system automatically adjusts its operating state according to the indoor temperature, the actual power consumption may be lower than this value. Assuming that the system runs for an average of 10 hours a day, the theoretical daily power consumption is 40 kWh.

3. Electricity bill calculation: According to the electricity price of 0.5 yuan per kilowatt-hour of electricity, the theoretical daily electricity cost is 20 yuan. However, considering that the actual electricity consumption may be less than 40 degrees, the actual electricity bill may also be less than 20 yuan.

2. Factors affecting actual costs

1. House insulation performance: A house with good insulation performance can reduce system operation time, thereby lowering expenses.

2. Outdoor temperature: Higher outdoor temperatures help the system get more heat from the air, reducing operating costs. Lower outdoor temperatures can lead to higher expenses.

3. Equipment efficiency and energy efficiency ratio: Efficient and energy-efficient equipment has lower operating costs.

3. Reference to actual cases

Some users have reported that in the case of a heating season of 120 days and a heating area of 100 square meters, the electricity bill for a day is about 14.4 yuan when using a full frequency inverter air source heat pump heater. The cost of the entire heating season is about 1,728 yuan, and the cost per square meter is about 17.2 yuan.

In summary, the cost of air heating for a day varies depending on several factors. In actual use, we can reduce heating costs by improving the insulation performance of the house, choosing appropriate equipment, and setting the indoor temperature reasonably. Therefore, when estimating the cost of air energy heating days, a variety of factors need to be considered to ensure the accuracy of the estimation results.