When replacing the electrical panel in your home, you must check that the new panel is the correct size. A licensed electrician might need to upgrade your electrical system using a larger panel to accommodate a variety of scenarios. Here we explain everything you need to know about sizing an electrical panel, understanding electrical loads, and knowing when it’s time to upgrade or replace the panel in your home.

Amperages and Electrical Panel Sizes

Electrical panels are available in several different amperages or sizes. The amperage of a panel determines the maximum electrical load or total number of available watts of electricity of a home. Ensuring that your electrical panel is large enough and has sufficient amperage is important for preventing electrical issues like tripped circuit breakers. A panel that is too small can be a major safety hazard because it poses a risk of the wires overheating and possibly starting a fire.

Many older homes have 60-amp service panels. While this was sufficient for the electrical loads of previous generations, it’s rarely sufficient for modern households. If you need to replace your electrical panel, you will have to install at least a 100-amp service panel. This is because 100 amps is the minimum required by the National Electric Code (NEC).

A 100-amp service panel may be sufficient for smaller homes with a few 240-volt appliances, but homes with central air or electric heat will likely need something larger. Most modern homes have 150- or 200-amp service panels. If your home is much larger, you will usually need a larger 400-amp service panel instead, especially if you have central air or electric heat. Furthermore, if you have multiple powerful large appliances, including a heat pump, EV charging station, and hot tub, you’ll need a higher amp panel.

The size of the electrical panel determines the total number of 120-volt and 240-volt circuits that can be wired into it. Most 100-amp panels can have around 20 total circuits or circuit breakers. Some 100-amp panels can support up to 42 circuits, which is the maximum allowed by the NEC for a 100-amp panel. The total number of circuit breakers a panel can hold also depends on how many 240-volt circuits there are in the home. This is because 240-volt circuits require a double-pole breaker that takes up two spaces. 120-volt circuits have single-pole breakers.

How to Know What Size Electrical Panel Your Home Needs

The only way to determine what size of electrical panel a home needs is to calculate its total electrical load, and this is something that should always be done by a licensed electrician. First, the electrician will determine the total square footage of the home and then multiply the square footage by three to determine how many watts are needed for all of the power outlets and lights. If your home has lots of outdoor lighting or independent circuits for holiday lights, they’ll also need to factor in the additional wattage of these circuits.

The next consideration is the number of small-appliance circuits in the kitchen. Small-appliance circuits are those along the countertops that are used for things like coffee makers, mixers, food processors, and toasters. In some cases, the microwave is on its own dedicated small-appliance circuit. These small-appliance circuits are always dedicated, which means that they don’t also supply power to the kitchen lighting. Each small-appliance kitchen circuit and the laundry room circuit adds 1,500 watts to the total load.

These calculations are generally the same for any home. However, they become more complex when considering the various major appliances and their respective loads. Every major appliance in a home is on a dedicated 120-volt or 240-volt circuit. This includes the washing machine, clothes dryer, refrigerator, electric water heater, oven, range, and EV charging station.

The wattage of these appliances can vary significantly depending on the size, age, and energy efficiency of the appliance. Some appliances like refrigerators and washing machines draw around three times the amount of current when starting than when running. This is part of the reason major appliances require a dedicated circuit. Otherwise, this start-up current would usually end up causing the circuit breaker to trip. Your electrician will need to look at the label or plate on each appliance to determine how many watts it uses both to start up and to run.

You might never have every appliance in your home running at the same time. This means that the electrician won’t factor in 100% of the wattage of all appliances. If the total load of all appliances exceeds 10,000 watts, the electrician will usually factor in anything over 10,000 watts at only 40%.

Finally, your electrician must account for the wattage of the HVAC system. A central AC or heat pump is usually the highest-wattage appliance in a home. However, if the home has an electric furnace or any other type of electric heating other than a heat pump, the electrician will add in the wattage of the heating system instead of the air conditioning.

How to Know If You Need to Upgrade or Replace Your Electrical Panel

You should always have an electrician inspect your electrical panel every year. If they find any issues, you should have your panel replaced immediately to prevent fire hazards and ensure your electrical system is safe. If your panel feels hot, makes a buzzing sound or shows signs of rust, corrosion, smoking or scorching, you should also immediately contact a licensed electrical company for an inspection. Consistent electrical issues like tripped circuit breakers and flickering lights also often indicate you need to have your electrical panel replaced.

A few other situations can also indicate the need for an upgraded panel or a dedicated circuit. If you’re building an addition onto your home, you should have an electrician evaluate your current panel to ensure it has sufficient amperage. Depending on the size of the panel and how many circuits your home has, your existing panel may also be full. This means that there isn’t space in the panel for another circuit breaker, so you won’t be able to add additional circuits. In this case, you may be able to just install a sub-panel for any new circuits. However, it will still depend on how many amps the main panel is.

Installing central air conditioning can also necessitate a higher amp panel as can adding new 240-volt appliances, such as an EV charging station or hot tub, or major systems, such as a home theater.

If you need to upgrade your electrical service or have your electrical panel inspected, 3 Mountains Home Services is here to help. We offer professional electrical repairs as well as EV charging installation, home generator installation and all other electrical installation services. For more information on our electrical and plumbing services or to schedule a service call in the Milwaukie area, give us a call today.

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