Watts vs Volts: Everything to Know About Measuring Electricity

Knowing the difference between watts and volts, as well as amperes (amps) and ohms, is crucial when working with any type of electrical system.

Repairing household wiring requires a solid understanding of electrical terms, and it is even a helpful knowledge base to have for everyday living. How many times have you seen a lightbulb printed with "100W/120V" and wondered how the two units of electricity relate? Are watts and volts basically the same thing? Can the two be used interchangeably?

Difference Between Watts and Volts

Watts and volts are not independent of each other. Watts cannot exist without volts since they are the product of a combination of volts and amps.

In basic terms and using a hydraulic analogy, volts are similar to water pressure and watts are similar to water flow rate.

What Are Volts?

A volt is the potential difference between two points of a conducting wire carrying a constant current of 1 ampere when the power dissipated between these points equals 1 watt.

The symbol for volt is "V."

Simplified, this means that voltage, compared to hydraulic water pressure through pipes, is the speed of the electrons as they pass a point within the circuit.

What Are Amps?

Amps (short for amperes) are the base unit for measuring the volume of electrons in an electrical circuit.

The letter "A" is the symbol for amperes or amps.

With the hydraulic comparison, amps would be a unit of measure indicating the volume of water moving past a certain point. Volume is quantity, not speed. A lightning strike is about 20,000 amps. A watch may draw one-millionth of an amp. Household electrical cables typically are rated for 15 amps or 20 amps.

What Are Watts?

A watt describes the rate of power flow. When one amp flows through an electrical difference of one volt, its result is expressed in terms of watts.

The letter "W" is the symbol for watt or watts.

Watts are derived from the formula V (volts) x A (amps)= W (watts).

What Are Ohms?

Ohms indicate electrical resistance. They measure the resistance that a device or material placed within the electrical circuit resists or reduces the electrical flow.

The Greek symbol for omega, resembling a downward horseshoe, also denotes ohms.

Wattage Ratings of Common Appliances

Understand Watts vs. Volts With the Travel Rate Analogy

Understanding the basic concept of rate is key to understanding watts vs. volts. An analogy often used is traveling and travel rate. As if you told a friend:

The car drove a total of 65 miles.

You've given the friend some information, but it's incomplete. There is no context. Did you drive those 65 miles in one hour, which is generally normal, or did it take you three days to drive 65 miles?

Consider a different way to talk about the vehicle trip to your friend:

The car for a total of 10 hours.

Discussing the length of the car trip, too, is incomplete. Did you drive across the U.S. in 10 hours—an impossible feat—or did you drive around 600 miles, which is more plausible.

How can you develop the perfect statement that takes both factors into account? That is called rate.

So, the formula V (volts) x A (amps)= W (watts) is similar to the car trip example. Both indicate rate. With the car, rate is equal to distance divided by time.

In electrical systems, amperage and voltage are useful sets of information. But wattage is an additional usual body of data because it combines the two to produce an indicator similar to rate or speed.