Finding out your home’s electrical service needs doesn’t have to be a hefty load
Electrical load is the total amount of power needed to run your appliances at a given time.
Understanding the relationship between amps, volts, and watts will help you relate the wattage of your electrical load to the amperage of your service panel.
Always ensure your electrical load calculation stays within 60% to 80% of your service panel’s total capacity.
Whether you’re wiring a house or undergoing an electrical upgrade on an older home, electrical load calculation is a crucial element of your planning. Calculating your electrical load will tell you the amperage needs of your electrical service, ensuring you have enough power to run your microwave, TV, and all of the other various appliances and electronics throughout your home.
While the equations we outline below can provide you with a good idea of what your home needs, it’s always best to review your numbers with a local electrician. It’s also important to remember that electrical work is hazardous territory that should only be attempted with the proper skills and experience. So, if you determine it’s time for an upgrade, don’t try to go it alone.
Here are two ways to calculate the suggested amperage you’ll need to power your home.
Add up the wattage of all general lighting circuits and the wattage rating for plug-in outlet circuits.
Add up the wattage for all of the year-round appliances in your home (excluding HVAC systems), such as the washer and dryer, dishwasher, refrigerator, and microwave.
Total up the wattage numbers from steps 1 and 2 and subtract 10,000 watts.
Multiply the result by 0.4 (40%).
Add the 10,000 watts back in.
Compare the wattage ratings for your air conditioner and furnace; add the larger number to your total since you’ll only be running one at a time.
Divide the resulting wattage by 240 volts (the typical main service for homes) to calculate the electrical load in amps.
Isolate the circuit that you want to measure.
Note the breaker’s size.
Multiply that figure by the circuit’s rated voltage to get the maximum load capacity.
For example, if you have a 20-amp breaker operating at 100 volts, its maximum load is 2,000 watts.
Calculations are based on the average wattage of common household appliances. Calculations rounded to the nearest whole number.
| Circuit System | Average Electrical Load In Watts |
|---|---|
| Cooling System | 3,000–4,000 |
| Electric Furnace | 10,000–50,000 |
| Washing Machine | 300–500 |
| Electric Dryer | 1,800–5,000 |
| Oven | 2,000–5,000 |
| Electric Stove | 1,000–3,000 |
| Water Heater | 1,125–4,000 |
| Dishwasher | 1,200–2,400 |
| Disposal | 500–1,500 |
| Garage Door | 400 |
| EV Chargers | 7,200 |
| Total | 28,525–83,000 |
| Average Square Footage | Average Electrical Load In Watts |
|---|---|
| 1,000 | 28.5–83 |
| 1,500 | 19–55 |
| 2,000 | 14–41.5 |
| 2,500 | 11–33 |
| 3,000 | 9.5–28 |
| 4,000 | 7–21 |
| 5,000 | 6–17 |
| 6,000 | 5–14 |
Since home service panels are measured in amps ranging anywhere from 100 to 400, you’ll need to calculate the amperage of your service panel versus the total wattage of your electrical load.
You’ll also need to factor in an additional safety margin of around 60% to 80%. In other words, you only want your electrical load to make up roughly 60% of your electrical system’s total capacity. Most experts advise that your safety margin should be no higher than 80%.
To perform your calculations, you need to understand the relationship between volts, amps, and watts. Here are the basic formulas:
Watts = Volts x Amps
Amps = Watts / Volts
You can use these formulas to calculate the capacity of your home's overall electrical service. For example, let’s say you’re working with a 150-amp service panel. Since the main service voltage that enters a home is typically 240 volts, the calculation would be:
240 volts x 150 amps = 36,000 watts
80% of 36,000 watts = 28,800 watts
This means that a 150-amp electrical service should not be expected to accommodate an electrical load of more than 28,800 watts at once.
So, where can you find the wattages of your devices and appliances for your electrical load calculation? Most appliances will have a little sticker on the bottom or back that shows how much power they use. You can also look up the technical specifications for the appliance online or in the user manual if you have it handy. In the meantime, here are some general ranges to reference.
While there are plenty of ways to improve your home’s energy efficiency, the last thing you want is to be constantly at odds with your circuit breakers or even leave your home vulnerable to electrical fires and other hazards.
When planning your home’s electrical needs, it’s always best to err on the side of caution and get a service panel with a higher capacity, potentially even higher than your 60% to 80% safety margin. Especially if you plan on staying in your home long-term, consider planning for the future and opting for the higher-amp service panel.
An electrical load is the total amount of power required to run all the appliances and electronics in your home, from your phone charger to your central AC system. This power is usually measured in watts. Home service panels come in varying levels of amps (usually 100 to 400) that can handle different wattages and electrical loads.
By calculating your electrical load, you’ll ensure you have a sufficiently-sized service panel and prevent electrical dangers from overloaded circuits.
