What is the purpose of an electrical panel?
What is an electrical panel?
An electrical panel (a.k.a. breaker panel) is a metal box with a door, usually built into a wall in an out-of-the-way corner of your home. Inside, you’ll find all your home’s breaker switches.
You can toggle breaker switches on and off. They’ll also shut off automatically when there’s too much electrical current running through them — that’s what they’re for.
Within the electrical panel, you’ll find a main circuit breaker that controls the power to the entire house. You’ll also see individual breakers, each responsible for providing the electricity to a specific part of your home. Each breaker should have a label that identifies the area of the house it controls.
Some older homes don’t have breakers; they have fuses instead. If you have a fuse box, you won’t see any switches on your electrical panel; you’ll see screw-in fuses. If your home still uses a fuse box, you may have difficulty getting insurance, or you may have to pay a higher rate. We’ll address fuses and home insurance further down the page.
The power to your home comes through an electrical meter outside, which routes power to your electrical panel. You can shut off this main feed of electricity using the main breaker in your electrical panel. Your main breaker also tells you the amperage of your electrical service (amperage is the strength of the electrical current).
Home electric services in Canada range from 60 to 400 amps. Most electrical codes mandate at least 100-amp service.
Home insurance providers are often interested in your home’s amperage. If it’s less than 100, you might need to update your system. Sub-100 amperage could make it difficult for you to find insurance for your home; at the very least, you’ll need to pay a higher rate.
How to locate your panel
Electrical panels are metal boxes, typically grey in colour. They’re usually embedded in a wall.
Electrical panels have doors (or at least, they should). Behind the door, you’ll find an assortment of wires and switches — those switches are your breakers.
Electrical panels are normally in an out-of-the-way part of your home. Basements, storage rooms, laundry rooms, or garages are all common places to install an electrical panel. In older homes, you might even have to look outside the house to find your panel.
In apartments, the most common places to find the panel is right inside the unit near the entrance or in the bedroom, behind the door.
Most homes have just one electrical panel, though some may have subpanels, especially homes that have multiple living units. See the common questions section for more on subpanels.
How does an electrical panel work?
Circuit breakers trip (that is, shut off) when the circuit is overloaded. They’re safety devices, meant to prevent damage to electrical devices or to the home itself. If the breaker didn’t trip and shut off the power, overloaded circuits could start fires or electrocute someone.
Each breaker controls one circuit; each circuit usually corresponds to a room or an area of the house. Power-hungry devices like electric ranges or air conditioners might have their own breaker.
A breaker is designed to carry a certain electrical load; if the electrical load grows too large for the breaker, it shuts off. This happens if you have too many devices plugged into one circuit, for example.
There are assorted sizes of breakers depending on how much electricity they need to handle. Like the home’s electrical service, individual breakers are divided by what amperage they can handle. Breakers range from 15 to 200 amps; most are either 15, 20, or 30 amps, though.
Breakers also have voltage ratings; a single circuit breaker is normally provides 120 volts — the typical amount needed for lights, TVs, etc. A double circuit breaker is rated for 240 volts. This is for the big appliances that draw a lot of power, such as a stove or electric dryer. Large, power-hungry appliances like stoves or refrigerators should each have their own dedicated breaker.
When the breaker trips, all you need to do is flip the switch to reset it. In older homes with fuse boxes, you can’t just reset it; you need to replace the whole fuse if it blows.
How much does it cost to change or upgrade an electrical panel?
The cost to upgrade your home’s electrical panel varies widely depending on the scope of the work, but you should expect to pay (very roughly) $2,000 – $2,500. That’s for 100-amp service, though. More commmonly, homeowners already have 100-amp service and need to upgrade to 200. The cost for that is approximately $3,500 to $5,000.
The only way to be sure about the cost is to have an electrician (or better yet: 3 different electricians) give you detailed quotes.
There are two reasons you’d want to upgrade your electrical panel: your service doesn’t provide enough power for your home, or you have fuses instead of breakers.
If your home has a fuse box, or your electrical service is below 100 amps, you should upgrade. Even if you already have 100-amp service, you might need to upgrade to 200- or 400-amp service, as many homes are running at capacity on 100-amp service.
If you’re not sure your electrical panel is enough, you can have an electrician estimate your service usage and tell you if you need an upgrade or not.
Electric Code Circuit Breaker Panel Box Requirements
Building codes govern electrical panels. For safety reasons, panels need to adhere to many standard requirements.
Building codes in Canada are different in each province and municipality, but generally speaking, they dictate:
- The height at which the breaker box must be.
- The location of the breaker box within the house. For example, they can’t be in a bathroom.
- The accessibility of the breaker box. As in, the box can’t be behind a bookshelf, and always must have clear space to open the panel door.
- The breakers must be clearly labelled. That includes their amperage ratings and which parts of they house they control.
There are tons of other technical electric code requirements for breaker boxes. But, unless you’re an electrician, you don’t need to worry; work on breaker boxes and electrical wiring should always be done by a qualified person.
What should you do when something goes wrong?
Tripped breaker
As mentioned earlier, a circuit breaker will trip if the circuit has become overloaded.
For instance, you’re using your blow dryer, while the TV and the desktop computer are running at the same time. Even if they’re all plugged into different outlets, they could be on the same circuit. This may result in too much power being drawn, and the breaker will trip.
If you’ve tripped a breaker, here’s what you should do:
- Turn off the power to the items that caused the breaker to trip. So, in this case, shut off your blow dryer, TV, and microwave.
- Go to the electrical panel box and open it.
- Find the tripped breaker. Of the many switches inside the electrical panel, you should see one that’s stuck in between the on and off positions, while all the others are still on. The odd one out is your tripped breaker.
- Flip the switch all the way to the off position, then back to the on position.
Now you should be able to use your electrical devices again.
Just remember, don’t use them all at the same time. Or you can move one of them to a different outlet. If you’ve shut off the offending electrical item, and the circuit breaker continues to trip, there could be another problem.
Insufficient capacity
If you have a breaker that trips often (or multiple breakers), it may be a capacity issue.
If it’s just one breaker causing problems, you can solve it by removing some electrical devices from that circuit and putting them on a different circuit. If it’s a case where you don’t have enough circuits (for example, all the outlets in your kitchen are on one circuit), you may need an electrician to rewire your breakers or add more circuits.
In some cases, an electrician can add subpanels or tandem circuits to spread power usage around more effectively.
However, it may also be that you’ve simply reached the limit of your home’s electrical service. If you have breakers tripping often, or you find that your electrical panel and the walls around it are warm to the touch, you might need to upgrade your whole electrical system to 200- or even 400-amp service — a big, potentially expensive job (but sometimes a necessary one).
In the short term, you can address capacity issues by not running too many devices at once (especially power hungry devices like HVAC systems, water heaters, or washer/dryer pairs.
Corrosion
Corrosion of electrical panels or the wiring around them is a sign that moisture is present. Moisture and electricity are not a good mix (obviously).
However, if you only find corrosion or rust on the metal door or frame of your panel, it may not be a significant problem — moisture in the air can cause rusting. Just sand the panel down, prime it, and re-paint it.
Corrosion on the breaker switches or electrical wiring is much more serious, though. It can be a sign that moisture is seeping into your electrical system, perhaps from the outdoor meter. If you see corroded wires or switches, call an electrician.
Short circuit
This situation is a bit more serious.
When one electrified wire (called a “hot” wire) touches a neutral or other hot wire, it will cause a short circuit. That can happen when mice or other animals damage the wiring, or when you plug in a device with damaged circuitry. It can be hard to find the cause of a short circuit.
Short circuits should immediately trip a breaker. If you reset a tripped breaker and it instantly trips again, a short circuit is most likely to blame.
If you think an electrical device is causing the short, shut off the breaker that controls power to that outlet. Check the power cord to see if there are any melted areas or other damage. Look at the outlet itself, and check for a burning smell or any dark discoloration. These are all signs of faulty circuitry. If you unplug the device and the breaker resets properly, that device was likely causing the short.
If you can’t find a specific appliance that’s causing the short, there may be some crossed wires in your electrical system. You should call an electrician to find and fix elusive short circuits.
Ground fault
Similar to a short circuit, a ground fault happens when a hot wire touches a ground wire, or any thing else that’s grounded. “Grounded” means electricity can flow through that object to the ground.
Ground faults often happen when electricity meets water. Say, for example, you’re using a hair straightener and you drop it in a filled sink. That would cause a ground fault and trip a breaker.
As is often the case in bathrooms, your outlet may have a ground fault circuit interrupter, or GFCI.
GFCIs are special devices that immediately cut power if they detect a ground fault (even faster than the breaker can).
GFCIs are part of electrical outlets and cut power to anything plugged into that outlet. You can identify a GFCI by the black and red buttons on the outlet. These buttons are for testing and resetting the GFCI.
If you trip your GFCI, unplug everything from it and press the reset button.
You should test your GFCI a few times a year. Just plug something in, turn the device on, and then press the test button on your GFCI outlet; it should immediately cut power to the device. If not, call an electrician to replace your GFCI.
The modern electrical panel is like a highway interchange for your house. It performs two important functions: it carries electricity to the outlets and fixtures in your home and it prevents overloads that could cause house fires.
The power to run your appliances typically begins at a power plant. It travels over long distances through high voltage wires–the tall towers that disturb many a homeowner’s views out their windows–through a transformer at a substation that steps down the voltage, and then through another local transformer, one of those big “cans” you may see on telephone poles along the road, where it steps down again. Finally, the electricity passes through the power lines to the meter at your home and into the breaker panel. The voltage that could be measured in the thousands at the beginning of its journey is rated at 120V or 240V at your panel—just the right amount to keep your home running.
Figure 1 shows a schematic of the typical breaker panel you will find in the basement, utility closet, or garage in most homes today. It is a gray metal box with a door. The main circuit breaker is on the top, which can shut off your home’s entire power supply. The power from your meter feeds into the main circuit breaker. Below the main circuit breaker are two vertical rows of branch circuit breakers that feed into sections of your home. Yours might be labeled “Dining Room,” “Kitchen Lights,” “Master Bedroom,” and so on. Appliances that use a lot of energy, like HVAC systems or electric stoves, may have their own breaker.
Figure 1
A panel cover protects the live mains that conduct power into the panel from the utility meter. Leave the panel cover closed at all times. Electricians are trained to work carefully around those dangerous mains when installing the Sense Home Energy monitor or making repairs to your system. The figure shows an electrical panel with the panel cover open, revealing the mains.
How Home Electricity Works
To understand home electricity, let’s start with basic terminology.
- Voltage: the electrical force that pushes electricity through a wire, measured in volts.
- Current: the flow of electrons through a wire, measured in amperes (amps).
- Power: the electrical power in a circuit equals voltage multiplied by current. The higher the voltage (the push) and the higher the current (the flow of electrons), the higher the power, which is measured in watts. 1000 watts = 1 kilowatt.
- Energy: The power an electrical device uses over time, expressed as kilowatt hours (kWh).
- Resistance: A measure of the opposition to current flow in an electrical current, measured in ohms.
Ohm’s Law describes the relationship between voltage, current, and resistance.
Voltage = Current (amps) x Resistance (ohms)
In other words, if you are “pushing” a high current through a circuit with high resistance, you need to pump the voltage. The human cardiovascular system provides a good analogy. The blood flow rate is current, the vessels and capillaries provide the resistance, and the heart provides that voltage to keep the blood flowing.
It’s helpful to know the terminology because the capacity of electrical panels is described in amps and volts, while the power draw of appliances and lights is described in watts, and your utility bills you for the power your home consumes in kilowatt hours.
How a Panel Controls Electricity
You may remember when circuits were protected by round, screw-in fuses that had to be replaced each time they were “blown.” New electrical panels have circuit breakers that don’t need to be replaced for the life of the breaker box. In older homes, the total current into the house was set at about 100 Amps, maximum. Newer homes that are bigger and have more electrical devices can require 200 Amps or more.
The electrical current divides into circuits in your house. Each circuit covers an area of the house and all the electric appliances in the area. Each breaker in the panel will trip at a different limit determined by the breaker’s amperage rating. This is also true for the main breaker. So in a 200A panel, if more that 200 amps are used across your home, it will trip the main breaker, minimizing the possibility of sparking or fire.
When a circuit breaker does its job shutting off an overloaded circuit, the breaker switch pops into the middle, between the on and off sides, which stops the current flowing through the breaker, similar to the way a light switch turns a light on or off. To reset your system–after turning off a couple of your appliances to relieve the circuit–you flip the breaker switch to the off position and back to the on position. It makes a distinctive clicking sound that most homeowners are familiar with.
If you expand your house, upgrade a major electrical appliance or buy an EV, you may need to upgrade your breaker panel to meet a high load. If your main breaker is tripping frequently, you may need to upgrade. It can cost $3,000 to $5,000 to upgrade a 100 amp capacity panel to 200 amps. Also, if your panel simply doesn’t have room for additional circuits, a licensed electrician may install a subpanel to expand it without changing the overall service level.
Once the power comes into your house and gets used by your electrical devices, the leftover electricity flows back out of the house via the mains.
Sense System Operation
The Sense Home Energy Monitor shown at the bottom of the panel in the figure gives your electrical system a Ph.D. in Electric Engineering—making it a very smart home. The Sense sensors clip around the main circuits inside the panel and read the electrical current 1 million times per second, while machine learning analyzes the patterns of devices turning on and off. The optional Sense Flex sensors can track solar power or up to two circuits of your choice, such as an HVAC system, dishwasher, or electric oven.
As you see electrical patterns in the Sense app, you can make practical changes to your home energy use that will save you electricity and money while minimizing the greenhouse gasses you create.
The Sense Home Energy Monitor can be installed in various panel configurations, including these:
- Split service systems up to 400A where service is provided via dual panels.
- Subpanels, provided that the monitor is installed in the main panel and the sub panels are downstream of this panel.
- Combination panels, using Sense’s re-designed slimmer sensors.
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Recessed or flush-mounted panels, using a specific installation process.
Efficiency Vermont has been in the business of helping Vermonters and anyone who will listen, save energy and money and decrease emissions for over twenty years. The nonprofit points to three benefits associated with the Sense monitor. First, you can make more informed choices if you an understand how much energy each electrical devices uses and when it uses it. For example, it can make you an energy “vampire” slayer. A vampire is any device that uses standby power even when it is “off”. Devices now are losing less and less standby power, but you can still save energy and money by using “smart strips” that shut off devices completely when they are not in use, like a TV set-top box or an audio power bar. A study done in 2015 by the Natural Resources Defense Council showed that you can save as much as a quarter of your energy use by slaying your vampires.
Second, you can find out which devices use the most electricity. Is it the fridge? You can decide to swap out an older model for a highly efficient Energy Star model or adjust how it functions to use less energy. Or you can find out where the lights are on when not needed and start paying attention to the off switches when you leave a room.
Finally, a Sense monitor can give you peace of mind while away from home. The Sense monitor will let you know if you left the fridge door open or forgot to turn off your stove.
Using Sense will make your home smarter. But even more important, it will make you and your family smarter and wiser about your energy use at home. At the very least, if you read this article, you will know much more about breaker panels than most people. It’s a start.