Does changing the fan speed or temperature of an air-con affect the amount of electricity used(electric bill)?

Answer 1

Yes, both affect the amount of electricity used and therefore the bill. External, real world machines (like an AC or a fan or a vacuum cleaner, whatever...) are powered by electricity under the action of moving electrons (current), which move because of a difference in electric potential (voltage). The higher the voltage, the faster the electrons will move through the device. The current represents the number of moving electrons through the device, and the total energy per unit time, or power, is the product of voltage X current (Watts or kilowatts, depending on the size of volts and amps). So, to power any moving device you need a voltage and some current. The more current you use, the higher your electric bill will be. It's like buying anything, the more you buy the more you pay..in this case your buying moving electrons from the power source (power grid, power lines or generator). If you run the fan faster, more electrons are needed. If you cool the AC to a lower temp, more electrons are needed to bring the temperature down to below room temp and keep it there (refer to the 2nd law of Thermodynamics for more physical details on cooling).

Answer 2

Changing the fan speed can change your electric bill. Slowing it down will make the system run longer but will remove humidity more effectively by reducing the evaporator temperature and reducing the air discharge temperature. Increasing fan speed will make the system run longer also due to the fact that the discharge air will be warmer. A/C units are designed for a 15-20 degree F temp across the evaporator, meaning about 300-400 CFM/ton of refrigeration.
I would not change fan speeds unless the system was designed for it or you actually know how much air you are moving. You can destroy your unit if not careful.

Answer 3

Yes it does. The slower fan speed takes less electricity to drive the fan. However, you have to be careful because the speed of the fan helps to determine the amount of air that travels throughout the house. You have to make sure that there is adequate air flow to move the air through your heating/air condition system. On my furnace, I have a two speed fan, the fan runs at the slower speed continuously and when the heating system comes on the fan changes to the higher speed automatically to move the warmer air rapidly throughout the house. The same applies to the air conditioner. If you don't have this type of system, then I would recommend that if you want to use the slower speed, then you should run the fan continuously.

Answer 4

Yes variable speed air handlers and raising the temp in summer will save you money. The variable speed air handler pulls more water out of the air and makes you feel more comfortable.