If you have an old regulator in your house: then you run it on 1 or 5, there is not going to be much difference in electricity expenditure. The old regulator is a kind of resistance.
They work like this:
When you do it on regulator 1, it puts more resistance in the middle of the power supply going to the fan (you can see in the picture above, point 1 has the most resistance). Due to the high resistance, the terminal waltz received by the fan is reduced and as a result the fan rotates slowly. Similarly, if the regulator is at 5, it puts zero resistance between the power supply to the fan, causing the fan to have more terminal waltz and the fan rotates faster. The problem of such resistance regulator-fan systems is that the resistance is like a load.
Suppose there is a bike, if we want to reduce its speed, then we will put 2 people on that bike, if we want to reduce the speed of the bike, then we will seat 3 people. This is reducing the speed but there is no reduction in petrol expenses.
Electronic regulator
But if a new type of regulator is installed in your home, then running the fan at 1 saves a lot of electricity and thus the bill will come down. The principle of electronic regulator is different. They use diac and triac instead of resistance.They also reduce or decrease the fan terminal waltz to reduce fan speed, but for this they do not work by sucking power inside them (as in resistance). They consume little energy inside themselves. They will take as much power from the supply as the fan needs to run at 1 or 5.
Caution: Many cheap electronic regulators are coming in the market, small protests are installed in them, they do not save much electricity.