The basics: what are watts, volts and amps?


If you are new to solar electricity, or any electricity for that matter, there are likely a whole lot of terms that are causing confusion. Don’t worry, you’re not dumb, the first time most people look at these terms and numbers it goes right over their heads too. It did to me.

Let’s start with the basics of electricity here (and the ones you will see most in dealing with solar electricity): watts, volts and amps.

What is a watt? defines a watt as: “the SI unit of power, equivalent to one joule per second and equal to the power in a circuit in which at a current of one ampere flows across a potential difference of one volt. Abbreviation: W, w.”

All cleared up? Probably not. A really basic definition of a watt is the amount of power provided by a circuit, basically the work performed. A basic incandescent light bulb requires 60w of power to perform its designed work, to illuminate. Make a bit more sense now?

What is a volt? defines a volt as: “the SI unit of potential difference and electromotive force, formally defined to be the difference of electric potential between two points of a conductor carrying a constant current of one ampere, when the power dissipated between these points is equal to one watt. Abbreviation: V”

What that is really saying is that volts are a measure of electrical pressure, how much electricity is being pushed through a circuit. Think of it like water pressure in a pipe. The amount of force with which the water is pushed through the pipe, either with a pump or through gravity, is similar to a volt in electricity.

What is an amp? defines an amp as: “the base SI unit of electrical current, equivalent to one coulomb per second, formally defined to be the constant current which if maintained in two straight parallel conductors of infinite length, of negligible circular cross section, and placed one meter apart in vacuum, would produce between these conductors a force equal to 2 × 10−7 newton per meter of length. Abbreviation: A, amp.”

Again, not likely very helpful. Aren’t dictionaries great? Let’s simplify a bit. What you really need to know is that an amp is the amount of electricity that flows past a given point. Again, think of the pipe. Where a volt was the amount of pressure forcing the water through the pipe, an amp is like the amount of water that is able to pass through the pipe.

The basic breakdown goes like this:

  • the watt is the power, or the amount of work that can be completed.
  • the volt is the amount of force with which the electricity is pushed through a circuit (like water pressure in a pipe).
  • the amp is the amount of electricity passing through a circuit at a given point (like the amount of water through a pipe).

Great, now we know the basic terminology, but how is it all connected? And how do we put this new found knowledge to practical use?

The relationship between the 3 looks like this:

Watts = Volts x Amps


Volts = Amps / Watts


Amps = Watts / Volts

Which means, if we remember our high school math, when we have any 2 of those units, we can figure out the third.

In real life what does that mean? Lets use a cooking example, because really, who doesn’t love food? The slow cooker in my kitchen runs at 180w on low and 120v. So if I am cooking up a pulled pork roast, on low at 180w using 120v, how many amps must be used? Based on the equations above:

Amps = 180w / 120v

1.5A = 180w / 120v

Keep in mind, this example is based on AC (alternating current), while a solar system will store power in DC (direct current) and doesn’t incorporate time into the equation. Since I’m pretty sure you’re close to, if not completely, overwhelmed by now, I will save those for another update soon.


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