Physics estimation problem (household electronics)

[joft]

Dear wannabe physicists, I have a simple estimation problem for you.

My tower fan used to be across the room from me. I had to keep it on a higher setting in order to feel the breeze. I just used an extension cord to move the fan closer, and turned the fan down to a lower setting.

Am I saving electricity this way?

(I haven't provided any quantities, such as the length of the extension cord, because (a) I don't know them (especially the energy usage of the various fan settings) and (b) any problem you ever work on in any job that makes any usage at all of your knowledge/skills will probably be given to you by some ignorant assholes who don't even understand which information is important to provide you with and which isn't, never mind what amount of accuracy each quantity should be measured with)

Most informative, practical, and prettily formatted post wins the thread

[Moochi]

Think about this:

The electricity might travel 100s (or even 1000s) of kilometres before it reaches your home. Do you think the extenstion cord is gonna make a difference now?

Yes, you are gonna save electricity.

[Senji]

yes

[sruon]

VxI=P

Assuming 230V, and 0.3 Amperes on Highest setting
Assuming 230V, and 0.2 Amperes on Middle setting

230x0.2=46W
230x0.3=70W

Difference: 24W

For 3 hours of use every day over a year:

(24x3)x365=26.28 kW.h

Assuming 0.12$ a kW.h, you're saving $3.15

For reference, total cost:

(70x3)x365=76.65 kW.h x 0.12 = 9.198 $/yr
(46x3)x365=50.37 kW.h x 0.12 = 6.044 $/yr

Cord extension is a non-issue because on such small scale the resistance of the cable is considered null.


(prz forgive me if there is any mistake, watt numbers are random but should be accurate.)

More accurate test would be to use an ammeter or a wattmeter and replace numbers by the one you find.