To determine how much wattage a device will use we can multiply the amps times the volts and the resultant product will be the wattage. The formula AMPS X VOLTS = WATTS is very important to people who work with electricity. Conversely, Watts divided by Volts will equal Amps and Watts divided by Amps will equal Volts.

To give an definition of how this works, let’s use the 100 watt light bulb mentioned earlier as an example. If the 100 watt bulb is for use in a residential home application and the electricity coming out of the fixture is known to be 120 volts then by dividing 100 watts by 120 volts we will arrive at the fact that our bulb draws .83 amps. For those countries that use 230 volt electricity, the formula still works and the amperage consumed would be calculated by dividing 100 watts by 230 volts (answer; .43 amps). Now let’s say the bulb is for use in a camper or RV that has a 12 volt battery system. We have to divide the 100 watts by 12 volts with the result that the bulb will now consume 8.3 amps of electricity. In all three of the above scenarios the bulb consumed 100 watts but the voltage and amperage varied in each case. To help us understand the concept a little better consider the dollar as equal to one watt. Which is more; a dollar bill, 4 quarters, 10 dimes, 20 nickles, or 100 pennies? They are all the same in value just as the 100 watts is the same amount of work or power consumption in each case.

This brings us to different voltages and the advantages and disadvantages of each. A 12 volt electrical system is a very safe system in terms of electrical shock because of the low potential for electrocution. 12 volt electricity just doesn’t travel through the human body very well. On the other hand, it doesn’t travel through a wire all that well either because the voltage (pressure, remember?) is so low. At 240 volts, we have the extreme potential for electrocution because the voltage (pressure) is 20 times that of the 12 volt system but, given the same load (appliance or fixture) at the end of the circuit, at 240 volts we only have to move 1/20 the amperage to operate the load. To solve this problem wire manufacturers created wire in different thicknesses (gauges) so that we could choose the wire gauge that would carry the voltage and current most appropriate to our application.

Because 12 volt electricity is so low in pressure, a larger wire is required to get our electrons to the point of use without creating a lot of heat (waste) along the way. By increasing the voltage wherever possible we can reduce the amount of amperage we have to push along the wire. Not only have we increased the pressure but we have reduced the volume when we raised the voltage. Therefore, we can use a smaller wire to carry the same wattage over a given distance if the voltage is kept high. The results of using a wire that is too small to carry the amperage expected of it is heat build up in the wire and loss of power at the other end. Some wire loss is normal but those in the know have established acceptable amounts of loss given in percents for the various voltages in common use today.