When comparing 110-volt with 220-volt circuits, you have to keep in mind that they both essentially do the same thing. That is, they carry the voltage to power electrical outlets. The equation is as follows: Power = Voltage x Current, with current measured in amps. When 220v wiring is used, less current is required than with 110v wiring. Power is measured in watts. Thus, to achieve 900 watts of power, 4.1 amps would be required with 220v wiring, whereas approximately 8.2 amps would be required with 110v wiring.
While both high amperage and voltage can mean danger in the event of an electric shock, the amount of amperage required for a fatal shock can be as little as 80mA. Since the human body has a constant resistance, higher voltage means higher current and therefore has a higher potential to kill. So although it's true that 220v requires less current to provide the same amount of power, as noted above, it can still carry much more current and poses a higher risk of serious injury.
Homes in the United States are wired for both 110v and 220v use. Regular power outlets found throughout a home are wired to 110v while only a few outlets are wired to 220v. They both are grounded; thus, they have safety features built into them. However, you should still use caution especially when you wire 220v.
110v Uses Versus 220v Uses
While most consumer goods, including portable electronics and most appliances, run on 110v power, some require 220v. Appliances, such as dryers, certain oven ranges, heavy-duty stationary power tools, and stationary compressors will likely require a 220v power source.
Basic Wiring of Both
A typical 110v wiring schematic requires three different wires: hot, neutral, and ground. With 220v wiring, both three and four-wire setups are possible. The red and black wires in 220v circuits carry 220 volts across each other but 110v in relation to the neutral, which is the white wire in a four-wire cable, leaving the green or bare copper wire for grounding the circuit. In every circuit with a white wire present, the white wire is always neutral.
When the wiring is complete, the respective outlets for 110v and 220v power are different as well. Standard 110v outlets are made for two or three-pronged plugs, the half-round opening accommodating the ground prong while the other two are different sizes being polarized so there can only be one way to insert the plug. With 220v outlets, there are either three or four holes per outlet. Three openings indicate that the 110 volts is not available in that circuit.
When wiring for 220v appliances or stationary tools in your home, you have to find out the current rating that will be required and use the appropriate size breaker to connect it to in the main panel. The size and type of cable will also be determined by the amount of current that will be drawn by the load. You'll have to make sure that you're not using a too-small gauge wire for the power needed. It is sometimes better when in doubt to refer to a certified electrician for the requirements in your local electrical code. Wrong size wiring could cause a house fire from generated heat in a too-small conductor.
At first, discussing the difference between 110v and 220v power can seem complicated, but remember that they are really two sides of the same coin. Supplying power to an outlet is the purpose of both, the main difference being that certain appliances and tools being plugged into those outlets require more power to run. With the power requirements of every home, 220 volts provides a way to decrease power consumption by half, making it much more efficient and affordable to operate large appliances and equipment.