Why does 220v cost less than 110v on my electric bill?

Question

Basically I want to know, with some math included, why 220v costs less than 110v.

Answer 1

The usage on your electric bill is measured in kilowatt hours, where "kilo" is a prefix meaning 1000, and the watt is a measure of power. Mathematically, power P (in watts) is equal to voltage V (in volts) times current I (in amperes):

P = V x I

Charges on your electric bill are not allocated by voltage, either 220V or 110V. The reason for this is rather simple. Somewhere near your home, your electric company has a transformer that converts the high voltage on the power lines down to the much lower voltage that is used in your home. The transformer is an electromagnetic device with two windings: the primary, which connects to the power lines, and the secondary, which is connected to your house. The ratio of the voltage on the primary Vp to the voltage on the secondary Vs is in proportion to the number of turns on the primary winding Np divided by the number of turns on the secondary winding Ns:

Vp / Vs = Np / Ns

The secondary winding has a centertap, that is, a wire that is connected to the midpoint of the secondary winding. The voltage across the secondary is 220V, but between the centertap and either side of the secondary it is 110 volts. These three wires are brought to your house.

The centertap connection is tied to earth ground at your breaker panel, and becomes the neutral wire for the power distributed in your house. The other two wires go to the circuit breakers, with half the circuit breakers on one wire and half on the other wire.

These two hot wires are 180° out of phase with each other. For a sinusoidal AC waveform, the voltage on one "phase" has exactly the opposite polarity as the voltage on the other "phase". Thus, the two voltages add together when you measure the voltage from phase to phase. In other words, the voltage from each phase to neutral is 110V, but from phase to phase is 220V.

Actually, the voltage measured is what is known as the root mean square (rms) of the sinusoidal waveform. It is an average value for the waveform. The peak voltage is √2, or 1.414 times the rms value. When we speak of a 110 Vrms 60 Hz AC voltage, the equation with respect to time t is:

V = (110 √2) sin (120 π t)

Because the two phases are opposite in polarity, the voltage from phase to phase is:

Vp-p = (220 √2) sin (120 π t)

Most high power loads, like an electric clothes dryer, electric cooktop or oven, electric water heater, or air conditioner operate from 220V power. Referring to the first equation above, this is so that only half as much current is required for a given load in watts. Reducing the current allows the electrician to use smaller sized wire, and also reduces the energy lost due to the voltage drop in the wire.

As I mentioned earlier, half of your (110V) circuit breakers and loads are on one phase, and half are on the other phase. If these loads were perfectly balanced and equal, there would be no current in the neutral wire flowing back to the centertap connection in the transformer. All the current would be from one phase to the other phase. However, it is impossible for the 110V loads to be perfectly balanced, because of the constantly changing number of light bulbs and appliances that are turned on at any time. So there will always be some current in the neutral wire.

The electric meter does not differentiate between power on 110V and power on 220V. Rather, it measures the total power consumed by the customer. Your electric bill charges for power by the number of kilowatt hours used, which is independent of the voltage.

Answer 2

I truly don't know which one in terms of electricity savings would be more cost efficient BUT since it would be uncommon to find a 220V outlet near one of your windows, when you take into consideration what you might pay an electrician for installation to run the wiring from your electrical box to the designated location as well as snaking the wire through the drywalls, the attic etc. I think the decision is pretty evident to go with 110v airconditioner. Food For Thought! And Hope Everything Goes as Well or Better than Planned/Expected...

Answer 3

IF YOU USE 220 FOR JUST DRYING CLOTHES, FOR EXAMPLE FOR MAYBE 2 HOURS A MONTH AND YOU USE 110 EVERY DAY AND MINUTE THEN NATURALLY 110 WILL COST MORE. CALL THE ELECTRIC COMPANY AND CHEW THE FAT WITH THEM ABOUT KILOWATT HOUR COST ETC. THEYLL EXPLAIN THE IR BILL.

Answer 4

In simple terms, most 220 volt equipment uses less amprage. Amps make the meter spin faster costing you more.

Answer 5

its an efficiency thing