When we decrease the speed of a fan through regulator .is it affect the cost / bill?

When we decrease the speed of a fan through regulator .is it affect the cost / bill?please explain the reason

if your fan is dc fan, for decrease speed you should decrease voltage. with decreasing the voltage through regulator, power and consequently cost will be down.

When we decrease the speed of a fan, the power consumption by it also decrease.
In regulator with resistance, the power saved is less than compared to the regulator with a triac. This is because in resistive regulators, a resistance is added in 'series' with the fan, thus keeping the voltage fixed. It reduces the current flow to the load. But it itself dissipates much heat, thus wasting some energy.
In regulator with triac, there is a break in voltage supply by triac firing, thus causing less energy supply to the fan. The triac doesn't hampers the supply by means of resistance, but by switching off the triac gate after a 'certain time', when the AC wave rises or falls from 0V. It itself doesn't wastes much energy and is the most efficient way of regulating a fan.

Thus, a regulator really saves electricity bill. As slow you run the fan, as low it consumes power...

Why some members are confusing the basuic concept.I am sharing my views in following lines if i am wrong please correct me:




In our homes due to parallel combination voltage across all appliances is same (220v or 230 v).So current may b different depending on the load.So it is clear now that only current will vary if our load will vary.So when we decrease speed of a fan through regulator, basically we are reducing the current to the load(fan).As a regulator is just like variable resistor so it dissipates more power(current) in form of heat when we reduce the speed of a fan.So there will be no effect on bill or cost .


Correct me if someone know the exact,simple and precise answer.

muhammad11 said:

So when we decrease speed of a fan through regulator, basically we are reducing the current to the load(fan).

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Yes. So current drawn from mains will be less, and total power used will be less. So cost will be less.

When the speed of the fan motor is reduced then its electrical power consumption is also reduced.
If you use a simple resistor in series with the motor then the total power and cost for the electricity are reduced because the current is reduced.
A modern motor speed control circuit is not a simple resistor, it uses Pulse Width Modulation and does not get hot, so ALL of the reduced power goes to the motor.

#muhammad11: So when we decrease speed of a fan through regulator, basically we are reducing the current to the load(fan).

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Yes, if you are using older regulator with variable resistance....

Was a variable resistance used to control the speed of a tiny toy fan?
Triacs have been used for controlling the speed of AC fans for many years.

godfreyl said:

Yes. So current drawn from mains will be less, and total power used will be less. So cost will be less.

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Dear less current will reach at load and remaining will be dissipated in regulator.So overall power will remains the same.so cost will be the same.correct me if you think i am wrong.

muhammad11 said:

remaining will be dissipated in regulator

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That part is wrong. The total current is less.
Do you understand the difference between voltage, current and power?

The resistor's job is to limit the current flow to the load. Since the load is getting low current, it will dissipate less power. But that doesn't mean the resistor have to waste the remaining power...
Resistor wastes only a fraction of "extra" power than the load...