Volts, Amps and Watts oh my! What we’re looking at here are different ways to talk about electricity. We’re not going to get hyper-technical, but we’re going to get technical enough for you to be able to understand the power you use, and hopefully get to a point where you’re ready to work with a solar array and system. In other words, this is a real world guide with useful examples, not a master class in electrical engineering. Feel free to take off your safety glasses and pocket protectors.
Explaining The Basics Of Electricity
Let’s get the main equation out of the way first:
Volts (V) x Amps (A) = Watts (W)
It can help to visualize these terms in relation to water. Volts are the water pressure, and amps are the flow rate (how fast or slow the water is flowing).
Most manufacturers will give you power ratings in watts. Sometimes they’ll get fancy and use kW. All that means is kilowatts, or, one thousand watts. It’s important to make sure, but at least in the United States most appliances are going to operate on 120 volts. If the manufacturer happens to leave out the amps, don’t worry, we can figure it out on our own with the formula above. If they give us Watts and Volts, we can divide Watts by Volts to get amps.
My blender uses 1200 Watts on 120 Volts. 1200 Watts / 120 Volts = 10 Amps.
Some experts may disagree, but for my purposes Amps are the way to go for thinking about electricity. My reasoning on this is simple: amps increase and decrease in a linear fashion (straight line, not an exponential curved line), meaning they are pretty predictable and easy to anticipate with mental math. To be practical in using amps though, we need to relate it to time. Buckle up friends, here we go.
If I use the blender from the example above, it uses 12 Amps when it’s running. BUT! It really means 12 Amp hours (Ah). So I could run that darn blender for an hour, and it would use 12 Amps from my batteries.
Let’s relate this to solar. Let’s say I have a 120 watt panel that outputs 12 volts. I know then, that 120 watts / 12 volts = 10 amps. So, if that panel was in full sun and was functioning 100%, it would put 10 amps in my batteries per hour… not too shabby for one little panel!
To carry these examples all the way through, let’s pretend that our 120 watt solar panel was bringing IN 10 amps to our batteries, and the blender was pulling 10 amps OUT of our batteries. If we ran the blender for a whole hour (smoothies in this house are very, very thin) and our solar panel was at peak production for the whole hour, our batteries will be at the same level when we finish as they were when we started. Solar smoothies, nice!
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