Understanding Your Home’s Electrical System

Understanding the home electrical system and being aware of common problems will help you keep things safe and working as they should, according to Peg Preble, a local electrician who teaches BBR’s Power to the People workshop.

Understanding your system

The first step is to understand at which point the power enters your house and becomes the homeowner’s responsibility rather than the utility’s. Electricity flows typically from an outside power line to the house via two 120-volt wires, each supplying the electricity for half of your house. A third wire is a neutral or return wire. According to Peg, “Most Boston neighborhoods still use overhead power, and the laws vary depending on your jurisdiction where public maintenance stops and your responsibility begins.”

Taking a tour of your home electrical system will help you see how it is set up, giving you a head start on understanding problems that may arise. Each home will have one or more breaker boxes (or fuse boxes) near the point of entry. Breakers (or fuses) control the distribution of electrical power to the various circuits in the home. The main breaker will cut all power to the home, and individual circuit breakers govern each circuit. Try to “exercise” the breakers every so often so they don’t get stuck. Practice turning each breaker off and back on, and familiarize yourself with the components of your electrical box.


A circuit is a length of electrical wire that starts from and returns to the electrical box. That wire supplies power to outlets, light fixtures, and appliances. If the amount of power going through the circuit breaker exceeds the limit for that circuit, or if a short circuit occurs, the breaker will trip and cut off power as a precaution against fire.

Recently, “smarter” circuit breakers (arc fault breakers) have begun to replace standard breakers and old-style fuses. Still, the responsibility lies with the people who live in the home to make sure no circuits are overloaded. A general rule is to have only one big-ticket item on a circuit. For example, your dryer, dishwasher, and space heater should not be on the same circuit! If your circuits overload regularly, consider having an electrician add more circuits. You can also consider adding an extra panel if you need more space in your breaker box.

Peg recommends that homeowners take some time to map out circuit paths. Knowing which fixtures and outlets are connected to which circuits will greatly assist any electrician who comes to work on the property. Recruit a family member or friend to help. Go room to room and plug a lamp or clock into each outlet, mapping which ones are on which circuit. Circuit maps are incredibly helpful for diagnosing an electrical problem and may save you money on an electrician bill.


Consider having an electrician upgrade your kitchen, bathroom, and outdoor outlets to GFCIs (ground fault circuit interrupters), especially if you have small children or elderly adults living in your home. If an appliance short-circuits or is used improperly, causing an imbalance between the power supplying the outlet and the return, a GFCI will cut power to the outlet to prevent damage or injury. While circuit breakers protect the wire, GFCIs protect the person.

Peg recommends surge protectors, which are integrated with many power strips and provide relatively inexpensive as “insurance” against electrical faults, especially for technology and computers.

If you have any electrical cords or light fixtures on the exterior of the home, make sure they are weatherproof, built to withstand moist environments, and on a GFCI-protected circuit.

Energy savings

The way we use electricity has changed over time and continues to change. Newer appliances are built with more energy-efficient technology, which reduces consumption. At the same time, we have added tiny, constant charges from devices such as phone chargers, laptops, small appliances, and indicator lights. One easy way to reduce overall usage is to replace incandescent and fluorescent lights with LED (light-emitting diode) bulbs. While these may be more expensive initially, LEDs are much more energy-efficient. Boston Building Resources has a variety of LEDs for sale at inexpensive prices, thanks to utility subsidies.

Pay attention to the enclosed and the exposed bulbs in your home. Heat shortens the lifespan of lighting products, so, to maximize the lifespan of your bulbs, choose fixtures that are not fully enclosed or use LED bulbs labeled “suitable for use in enclosed fixtures.”

Keep in mind that, in many cities and towns, including Boston, it is not legal for a homeowner to change a hardwired light fixture, ceiling fan, or receptacle. Only a licensed electrician, who is familiar with the electrical code and required safety precautions, is permitted to do this.


When evaluating an electrical problem, examine the box to see which breaker has been tripped. Then turn off or unplug all the items connected to that circuit. If the breaker will reset, reintroduce the items one by one to see if you can isolate the problem. If you continue to have trouble, call a licensed electrician.

—Fizzah Shaikh