Electrical wiring in your home is not something to be taken lightly. If you're planning to move into a new home or upgrade your old house, it's important that you understand the electrical load capacity of your home.
Understanding the load capacity will help you plan and manage the distribution of electricity throughout your house. A qualified electrician can help install new or upgraded electrical services if needed. Keep reading to understand how to calculate electrical load capacity for your home:
What Is Electrical Load Capacity?
Electrical load capacity is the total amount of current a wire can handle. A home requires a certain electrical load capacity to power all of its appliances and electrical devices safely. If your household is going through frequent blackouts, you need to add up the wattage on each appliance and device so that they fall below the limit for which your wiring is rated.
How do you know if your current electrical service is adequate? The total electrical capacity of electrical service is measured in amperage or amperes. When making significant electrical additions to your home, everything that uses electricity to run should be calculated to find the electrical load.
The electrical load is measured in wattage or watt/hours. The electrical load capacity is the total amount of electric current your household wiring can handle safely at one time before it presents a hazard.
The national electrical codes are the basis to ensure that wiring is safe and meets safety requirements for a given location. The code states that individual branch circuits in a modern residence should be at least 40 amps, equivalent to eight standard 15 amp outlets per circuit.
Why is Electrical Load Calculation Important?
Finding the correct electrical load capacity by adding up all of the wattages for appliances and devices is important. Not only will they be affected if you overload your circuit, but so will your safety. By finding the electrical load, you'll be able to determine whether you need to change your electrical service. It will tell you the power supplied in the home is not enough for your electrical use.
The electrical service is commonly measured in amps, and you can find the amount provided on your electrical power bill, which states that it is 120 volts, 20 amps. Best licensed electricians recommend dedicating a single circuit to appliances that consume so much energy, such as refrigerators, washing machines, air conditioners, and dishwashers to avoid overload. You can avoid spending money on repairs due to overloading by having basic knowledge in calculating your electric load.
How to Find Electrical Load Capacity
Calculating how much power your home needs is calculating the amperage load of all the various appliances and all the light fixtures. Find the total wattage of all appliances and devices plugged into a circuit breaker box by consulting their labels; look for the number of watts (W) they use.
Calculating the wattage of a home isn't an easy task, but there are several items that can be checked if you're looking to find the amount. Although checking all of your appliances and devices is ideal, oftentimes, it's impossible or inconvenient to do so, which is why estimations will have to be made based on the average wattage of similar appliances.
If you want to check your home's electrical load capacity without finding out its wattage, try using a device called an electric load calculation cord available for purchase at hardware stores. If you have an electrician install it, they can then show you how to find your circuit breaker box's amperage and calculate the wattage of each appliance or device on a circuit.
Once you know how many amps your load calculation cord reads, multiply it by 120 to find its voltage and then multiply that number by the amperage of each appliance you plan to plug into that circuit. If your total is higher than the circuit's capacity, you will need to unplug one or more devices before it can safely deliver power where your family needs it.
The circuit works like how the water flows from a pipe. The water pressure is in volts and the water flow rate is in the amps. The water wheel represents watts which depend on the pressure. You can use these formulas to calculate individual circuits' capacity, electrical loads, and the entire electrical service panel.
How to Calculate Your Home's Electrical Load
Different homes need different amp services, and you can do a little math to figure out what kind of electrical load your house needs. For example, a 60-amp service is inadequate for a modern home, while a 100-amp service is good for a home of less than 3,000 square feet without central air-conditioning and electric heat.
In that case, a home larger than 2,000 square feet with a central air-conditioning and electric heat may need a 200-amp service. A 100-amp is large enough to power a small to moderate-sized home's general branch circuit breakers, plus one or two electric appliances, including a water heater and clothes dryer.
This service may also be sufficient for a home under 2,500 square feet if you're running your heating appliances on gas. 400-amp service is recommended for large homes with all-electric appliances and heating and cooling equipment. It's recommended where the expected electric heat load be over 20,000 watts.
How to Add Capacity to Your Electrical Load
Installing a new circuit isn't that difficult, but ensure your service panel can handle the extra load before you begin. This is because a service panel with too many circuits can be dangerous. Fuse boxes rarely have space for new circuits, so replace the fuse box with a circuit breaker if you have a fuse box and need new service.
If there's a slot in the breaker box, you can remove an open space or a knockout and install a new breaker and run the cable to it. If there's no open space, the local electrical codes might allow you to replace a single breaker with a tandem breaker.
Electrical Load Box Sizes
The size of your electrical load box will determine your home electrical capacity. The electrical load boxes come in three categories. These include:
Small Fuse Box (15 amps)
Small load boxes are small enough to fit an electrical panel outside of your home. You can also find this fuse box in older homes where their wiring has not been upgraded. It can supply power to only one 240-volt appliance such as an oven and clothes dryer.
And since many homes have more than one such appliance, this fuse box is inadequate for a home of 1,200 square feet or more. You can upgrade to a larger size if you plan to add more circuits to your electrical equipment.
Medium-Sized Service Panel (30 amps)
This box is often found in homes that were built before electric dryers and dishwashers become common appliances. This fuse box can supply power for up to three 240-volt appliances such as clothes washers, stoves, and dryers.
It supplies electricity to the entire home except for lighting circuits which are fed from a separate panel. It's also the minimum panel amperage required by the national electrical code.
Large Service Panel (100 amps)
This is the box that most homeowners install when adding new circuits or upgrading their electrical systems. This can be fed from either a sub-panel or direct from the main electrical circuit breaker panel. It will supply power to more appliances than any smaller fuse panels, but it's still limited to 100 amps.
This type of fuse box might be required in a home that uses large electrical appliances and includes heating and air conditioning equipment. Upgrading to this fuse type can give you more flexibility to use more circuits without worrying about overloading the system.
How to Inspect a Service Panel
It's always good to be careful when carrying out electrical wiring; kids shouldn't be around the panel except for adults. Make sure you firmly attach any exposed cable to the wall and clamp it tightly to the knockout holes in the panel.
If you find any hopeless tangle, call in an electrician for an evaluation. Also, call in a professional if you find melted wire insulation, any signs of fire, and extensive rust. Make sure you oversize an electrical service to make future expansion possible.
FAQs on Calculating Electrical Load Capacity for a Home
How do you calculate electrical panel load?
You calculate the total load on the breaker panel by adding the amperage ratings from each circuit breaker then multiply that sum by 120 volts.
Are 200 amps enough for a house?
This depends on the size and how many appliances you will be powering. The more lights, outlets, fans, and ovens you plan to use simultaneously, the more electricity your panel will need to supply safely.
What are the maximum amps in a breaker panel?
The electrical service maxes out at 200 amps when the home has both air conditioning and electric heating. Heating capacity can go as high as 250 amps. If you plan to install an electric heating system, contact your local utility company for the maximum amp rating for your specific zone.
Final Thought on Calculating Electrical Load Capacity for a Home
Electrical connections can confuse you sometimes, but it's not scary or complicated once you know how it works. You need to understand the basics, and you'll be fine. Always know that overloading your circuits can be hazardous not only to your family but the entire community.