Basic Understanding of Home Electricity

In most modern homes in the United States, the public utility power lines feed a 200 Amp service to the home. This electrical service is fed through the circuit box in your home so it can be safely distributed throughout your house. Some older homes may have a 60 or 100 Amp service and large homes may have a 400 Amp service.

Your circuit box (panel) is a metal box composed of various sized circuit breakers (circuits) each usually 15 Amps up to 30 Amps. Each circuit breaker feeds a specific amount of power as 110V/120V of electricity to various parts of your home. These circuits are a safety measure to protect your home from electrical overloads and potential fires.

• Note: At any time, if you are unsure about the meaning of any of the Electrical and Lighting terms used in this article, our Lighting Terminology page may be of assistance.

As electricity is used in a room or area of the home serviced by a specific circuit breaker, each device draws different power for its needs. As you turn on more and more devices, they each draw a certain amount of Amps through the circuit. When too many devices are turned on and their power needs exceed the limits of the circuit breaker, the breaker will "trip" and stop the flow of electricity to that area of your home. You then need to reset the breaker at the circuit box to restore electricity to that area. It is also wise, at this time, to turn off some of the devices that were drawing power to avoid tripping the circuit again.

For a short time, a circuit breaker can handle a 100% draw of electricity through it. So, for a 15-Amp circuit, you can draw 15 Amps of power for a short time. But, if the draw of electricity extends beyond 3 hours of continuous use, the circuit will trip. For extended uses of electricity, your circuit breaker, for safety, will only supply 80% of its capacity continuously. So, your 15-Amp breaker is usable for 12 Amps of continuous service.

To figure out the total electrical needs of the devices in a room, you can use a simple formula to determine the number of Amps each device needs and then you can add up all of the device's needs to see if your current circuit breaker can handle the load.

The formula is:
(Device Watts) / (AC Voltage) = (Number of Amps Required)
or, (Watts) / (Volts) = (Amps).
 

Our constant, for the most part, is that AC outlets receive 120V of AC electricity supplied to them. Some examples of the individual device power needs calculations are:

• 60W Lamp = 60W / 120V = 0.5 Amps
  (3) 60W Lamps = 3 * 0.5 Amps = 1.5 Amps needed
• 1500W Hair Dryer = 1500W / 120V = 12.5 Amps needed
• 200W LCD TV = 200W / 120V = 1.67 Amps needed
   

It is important to note that even though a room is serviced by a 15-Amp breaker and you might have more than 20 Amps worth of devices in the room, you will rarely use ALL of the devices simultaneously in that room. Hence, your circuit will not trip.

The wiring in your home also plays a part in keeping your house safe from fire and/or overload. Depending on the power needs of specific areas of your home, different thicknesses, or gauges, of wires are used in conjunction with the circuit breakers to provide a level of safety. For example, a 14-gauge wire supports the power supplied by a 15-Amp circuit but you would use a thicker 12-gauge wire to support a 20-Amp circuit.

For minimal power needs, a 15-Amp circuit may supply enough power for a whole bedroom for lights, TV, clock, etc. But, in your kitchen where you have lots of electric powered devices such as blenders, microwave ovens, toasters, and coffee makers and such all working together, (2) 20-Amp circuits may be used. And, for large appliances such as an Air Conditioner unit, you may have a single dedicated 30-Amp circuit to supply enough power and protect you.

Power is supplied to our kitchens and other rooms in the home, for the most part, at 120V AC (alternating current) from our circuit box. For larger appliances such as an Air Conditioner, power requirements may be pushed at a higher 240V.

To be safe, prevent fires, and work efficiently with the LED lighting products in our kitchens, we use a DC (direct current) power supply to reduce/transform that 120V AC electricity to a safe 12V DC (direct current). If you are electrocuted by 120V AC current, it can kill you. As LED lighting is low voltage, you cannot just plug your LED lights into any 120V AC wall outlet. You need an AC to DC transformer to make your lighting installation safe and reduce the chances of a fire breaking out. You can still get shocked by a DC transformer but it probably won't kill you.

For our low voltage LED lighting, the 12V DC transformer, also called a power supply or driver, pushes electricity in one direction for a distance of 20'. The transformers are also limited to supplying 6W-60W of electricity depending what your power needs are for an area to be lighted.

See our article, How many lights can I install? to determine the number of lights you can install in your space and the power requirements.