UNDERSTANDING YOUR HOME'S ELECTRICAL SYSTEM
Electrical Basics
Understanding watts, volts, amps, and kilowatt-hours makes it easier to plan home power projects. This guide explains the numbers in plain English and shows how they relate to the appliances, batteries, generators, and other equipment you may be considering.
Watts, Volts, Amps, and Kilowatt-Hours
These four measurements explain most of the electrical numbers you will encounter when planning a home power project.
Volts (V), Amps (A), and Kilowatt-Hours (kWh)
Volts describe electrical pressure, while amps describe the flow of electrical current. Kilowatt-hours measure how much energy is used over time. Your electric bill is based largely on kilowatt-hours.
Watts (W)
Watts measure how much electrical power a device uses while it is operating. A 100-watt light uses about twice as much power at a given moment as a 50-watt light.
THE NUMBERS THAT MATTER
How Watts, Volts, and Amps Relate
These measurements are connected. Understanding that relationship helps you make sense of the electrical requirements shown by our calculators.
Volts
Electrical pressure that pushes current through a circuit.
Amps
The amount of electrical current flowing through a circuit.
The amount of electrical power being used. For basic calculations, watts can be found by multiplying volts by amps.
Watts
HOW THE NUMBERS WORK TOGETHER
How These Numbers Help With Home Power Planning
When you plan for backup power, solar, batteries, or a generator, these numbers tell you two important things: how much power your equipment needs and how much energy it will use over time.
Starting Power
Some appliances need extra power when they start. Motors in refrigerators, air conditioners, pumps, and other equipment can briefly require much more power than they use while running.
Running Power
Once an appliance is operating, its running watts tell you how much electrical power it is using. Adding the running watts of the equipment you want to operate helps determine your power requirement.
Kilowatt-hours tell you how much energy is used over time. This becomes especially important when estimating how long a battery can run your home or how much energy a solar system needs to produce.
Energy Over Time
WHY THIS MATTERS
How the Numbers Work in a Real Home
You do not need to be an electrician to understand the basic calculation. The relationship between volts, amps, and watts helps show how much power an appliance needs.
Start With Volts
Most household appliances in the United States use about 120 volts. Think of volts as the electrical pressure available to the appliance.
Find the Amps
Suppose an appliance draws 10 amps while it is running. Amps describe how much electrical current is flowing to the appliance.
Multiply volts by amps to find watts. 120 volts × 10 amps = 1,200 watts. That appliance is using about 1,200 watts while running.
Calculate Watts
A SIMPLE EXAMPLE