Solar Power Amp Hours VS Watt Hours Explained

In this short guide where we explain the difference between solar power amp hours vs watt hours. This is an important topic for anyone building DIY solar system, and we will use the most simple language to explain this.

If you need some basics understanding of electricity, we have a ultimate guide where we break down volts, amps, watts, resistors. It’s written so easy to understand for college student and even a 7th grader. Click here to view

Otherwise, let’s continue.

Major Difference Between Amperage Hour And Wattage Hour

Knowledge Refresher

Watt Hour is total energy output generated over time.

Amp Hour is total electric charge current passing a point.

A better visual analogy we can give this the following:

amperage wattage analogy

Referenced ​waterheatertimer.org

What Is Amp Hours?

Amp Hours (Ah) is the amount of current (amps) over time.

For example: 1 Ah = 1 amp for 1 hour

Analogy: Picture a car going 45 mph, after 1 hour the distance traveled is 45 miles. If something is 45 amp running for 1 hour, that’s 45 Amp Hours.

Amp Hours is also the unit used to measure battery capacity

Why Is Amp Hour Spec Important?

Adding deep cycle 12V batteries to your solar system is a key component, and battery capacity is rated in Amp Hours, aka how many Ah can the battery store in a battery.

However, Amp Hour alone can’t tell you everything until you look at the battery’s Watt Hour capacity.

So where does Watt Hour comes into play?

What Is Watt Hour?

Watt Hour (Wh) is the amount of Watts over time, it’s quantify the amount of energy

Watt Hour = Volts X Amps X Hours

For example:

1 Wh = 1 watt for 1 hour

  • 20 Watt light bulb on for 1 hour, that’s 20 Watt hours
  • 20 Watt light bulb on for 2 hours, that’s 40 Watt hours

Most batteries are 12V, so it will be:

12V X 100A X 1 hrs = 120 Watt Hour

Battery Capacity = 12V X 100 Ah = 1200 Watt Hour

This is a critical part of the equation when we design our solar system based on how much we use.

We can use the Watt Hour and reverse the calculation to find voltage required for a system to size our wires.

How Much Is 1 KWh ?

1 Kilowatt Hour is simply 1000 Wh, and 40 KWh is 40000 Wh

Average household in the US uses up to 19000 kWh a year, that’s 52 KWh a day.

Jeunkong Tai

Recent college graduate from the University of Kansas with an electrical engineering degree and bilingual in Chinese and English. I've learned about solar panels just by being around friends that have them on their home rooftop, and have gained knowledge by helping out on some DIY projects.

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