⚡ Electrical Load Calculator
Size a home's electrical service the NEC way. Enter the square footage and major appliances, and get the calculated load in volt-amperes, the service amps, and the panel size you need. Free, no sign-up.
An electrical load calculator finds the total demand a dwelling places on its service, so you can size the panel. Using the NEC Article 220 standard method, it adds the general lighting load (3 VA per square foot), the small-appliance and laundry circuits, the range, the dryer, fixed appliances, and the larger of heating or cooling, applying each load's demand factor. The core of it:
How to calculate a dwelling load in 3 steps:
- Enter the living area and the number of small-appliance and laundry circuits.
- Add the range, dryer, fixed appliances, and your heating and cooling.
- Click Calculate for the total VA, the service amps, and the recommended panel size.
For example, a 1,500 sq ft home with a 12 kW range, an electric dryer and 6 kW of heat calculates to 24,100 VA, about 100 amps at 240 V.
Electrical Load Calculator
Enter your home's area and appliances, and get the service load and panel size.
Get Your Service Size Right,
the NEC Way
Guess the service size and you either trip the main breaker or pay for a panel you never use. This free calculator turns your home's square footage and appliances into the calculated load in volt-amperes, the service amps, and the panel size you need, all by the NEC Article 220 standard method.
⚡ Calculate My LoadA Home's Electrical Load Is Demand, Not Nameplate
If you added up the nameplate rating of every appliance in a house, you would get a number far larger than the service it actually needs. Nothing runs everything at once. The NEC load calculation in Article 220 turns that pile of ratings into a realistic figure by applying demand factors, and that figure is what sizes the service and the panel.
The calculator above uses the Article 220 standard method, the itemized approach taught in every apprenticeship. It starts with a general load based on floor area, adds the kitchen and laundry circuits, applies a demand factor, then layers on the range, the dryer, the fixed appliances, and the larger of your heating or cooling. Divide the total volt-amperes by 240 volts and you have the service amps. Round up to the next standard panel and you have your answer.
That result tells you whether a 100, 125, 150 or 200 amp service fits the home. Get it wrong on the low side and the main breaker trips or the inspector rejects the plan. Get it wrong on the high side and you pay for copper and gear you never use.
How the Electrical Load Calculator Works
Six inputs, grouped the way the code groups them. Enter what the home has, leave anything it does not have at zero, and read the service size.
Enter the Floor Area
The living area in square feet. The code uses 3 VA per square foot for general lighting and receptacles. Leave out the garage, the porch, and any unfinished space not adaptable for future use.
📐 Outside dimensions of habitable space, garage excluded.Set the Circuits
At least two small-appliance circuits for the kitchen and one laundry circuit, each worth 1500 VA. Add more small-appliance circuits if the kitchen has them.
🍳 Two is the code minimum for the kitchen.Add the Range
The nameplate rating of the electric cooktop or range in kilowatts. A single range up to 12 kW counts as 8000 VA under Table 220.55. Leave it at zero for a gas range.
Add the Dryer
The nameplate of the electric dryer in volt-amperes. The code uses 5000 VA or the nameplate, whichever is larger. Gas dryers draw almost nothing, so leave it at zero.
🌀 5000 VA is the floor for an electric dryer.List the Fixed Appliances
Water heater, dishwasher, disposal, built-in microwave. Enter each one's volt-amperes. If four or more are present, the calculator applies the 75% demand factor automatically.
🔌 Four or more triggers the 75% reduction.Enter Heating and Cooling
Electric heat in kilowatts and air conditioning in volt-amperes. Only the larger of the two counts, since a house does not heat and cool at the same time. Calculate to read the total VA, the amps, and the panel size.
🌡️ The bigger of heat or AC wins.How a Dwelling Load Is Calculated
The standard method walks through the loads in a set order, applying each load's own demand factor before adding it to the total.
First comes the general load. Multiply the floor area by 3 VA per square foot, then add 1500 VA for each small-appliance and laundry circuit. For a 1500 square foot home with two kitchen circuits and one laundry circuit, that is 4500 plus 3000 plus 1500, or 9000 VA.
That general load gets the Table 220.42 demand factor: the first 3000 VA at 100%, and the remainder up to 120,000 VA at 35%. Our 9000 VA becomes 3000 plus 35% of the remaining 6000, which is 3000 plus 2100, or 5100 VA. The code recognizes that all the lights and receptacles never run at full draw together.
Then the large loads are added at their own factors. A single range up to 12 kW is 8000 VA (Table 220.55, Column C). The dryer is 5000 VA or its nameplate, whichever is larger (220.54). Four or more fixed appliances share a 75% factor (220.53). And only the larger of heating or air conditioning counts, because they are noncoincident loads (220.60).
Add the demanded general load to those large loads for the total volt-amperes. Divide by 240 volts for the service amperes, then choose the next standard service size. The formula in short: total VA divided by 240, with the general load derated first.
The NEC Demand Factors, in One Place
Every reduction the standard method allows, with the code section behind it. These are what separate a calculated load from a raw nameplate total.
What Pushes a Home Toward 200 Amps
Two homes of the same size can land on very different services. A handful of loads do most of the work.
The heating system is usually the swing factor. Electric resistance heat is taken at 100% with no demand reduction, so 10 kW of baseboard adds a full 10,000 VA, more than the range and dryer combined. A home with gas heat and a small air conditioner may calculate at half the amps of the same home with electric heat.
The fuel choices across the kitchen and laundry matter almost as much. An all-electric home with an electric range, an electric dryer, and an electric water heater stacks up three large loads. Switch those to gas and the calculated load can drop from a 200 amp service to a 100. Floor area matters least of the major inputs, because the general load is so heavily derated. Doubling the square footage adds far less than adding electric heat.
Standard Method vs Optional Method
Article 220 offers two ways to size a dwelling. This calculator uses the standard method. Here is how the two compare.
From Calculated Load to Panel Size
The volt-ampere total is only the middle of the job. Turning it into a service size takes two more steps.
Divide the total VA by the service voltage, normally 240 volts for a single-family home on a 120/240 volt service. A 24,100 VA load is 100.4 amps. Then round up to the next standard overcurrent size. Common residential services are 100, 125, 150 and 200 amps, so a 100.4 amp load lands on a 125 amp panel once you account for the next standard size above the calculated figure.
For new construction, many electricians install a 200 amp service even when the calculation allows less, because the marginal cost is small and it leaves room for an electric vehicle charger, a heat pump, or a future addition. The calculated load is the floor, not a target. Pair this figure with the wire size calculator to size the service conductors, and the voltage drop calculator to check a long service run.
Why the Service Size Has to Be Right
An undersized service and an oversized one both cost money, in different ways.
Worked Load Calculations
Three dwellings, three very different services, all by the standard method.
Load Calculation Best Practices
A few habits keep a calculation defensible at plan review and useful for the life of the home.
Use appliance nameplates, not catalog estimates, for the range and dryer, and keep a copy with the calculation. Run the numbers both ways when a dwelling qualifies for the optional method, and use whichever gives the smaller compliant result. Always size for the heating or cooling load that is larger, never both. And when in doubt between two standard service sizes, step up rather than down, since the cost gap is small and the future is rarely lighter on electricity. Above all, treat the output here as a planning estimate and have a licensed electrician confirm the final design against the locally adopted code.
When This Calculator Is the Wrong Tool
It is built for one common case. Outside that case, treat the result with care.
This is a single one-family dwelling calculation by the standard method. It does not handle apartment buildings of three or more units, which use the multifamily demand factors in Table 220.84, nor commercial, industrial, or farm services, which have their own rules across Article 220. It assumes a 120/240 volt single-phase service and a single electric range and dryer. It does not size feeders to subpanels, calculate the neutral load under 220.61, or apply the optional method. For any of those, use it only as a first rough check, and rely on a stamped calculation for the real design.
Load Calculation Terms On This Page
- Connected Load
- The sum of every load's nameplate rating, before any demand factor. Always larger than the calculated load.
- Calculated Load
- The load after demand factors are applied. This is the figure that sizes the service and the feeder.
- Demand Factor
- A percentage that reduces a load to reflect the fact that not all equipment runs at full draw at the same time.
- General Lighting Load
- 3 VA per square foot of dwelling area, covering general lighting and ordinary receptacle outlets.
- Small-Appliance Circuit
- A 20 amp kitchen circuit for countertop receptacles. At least two are required, each counted as 1500 VA.
- Volt-Ampere (VA)
- The unit of apparent power used throughout load calculations. At 240 volts, 240 VA equals one amp.
- Noncoincident Loads
- Two loads that cannot run at once, such as heating and cooling. Only the larger is counted (220.60).
- Service
- The conductors and equipment that deliver power from the utility to the premises wiring, rated in amperes.
- Feeder
- The conductors between the service equipment and a panelboard or subpanel.
- Standard Method
- The itemized dwelling calculation in Article 220, Part III, applying each load's own demand factor.
- Optional Method
- The simplified dwelling calculation in 220.82: the first 10 kVA at 100%, the remainder at 40%.
- Table 220.42
- The general lighting demand table: the first 3000 VA at 100%, the remainder up to 120,000 VA at 35%.
- Table 220.55
- The cooking-equipment demand table. Column C gives 8000 VA for a single range up to 12 kW.
- Article 220
- The NEC article governing branch-circuit, feeder, and service load calculations.
Frequently Asked Questions
How do I calculate residential electrical load?
Start with the general load: 3 VA per square foot of living area, plus 1500 VA for each small-appliance and laundry circuit. Apply the Table 220.42 demand factor, the first 3000 VA at 100% and the rest at 35%. Then add the range, the dryer, the fixed appliances, and the larger of heating or cooling. Divide the total volt-amperes by 240 for the service amps.
What size electrical service do I need?
Calculate the total load in volt-amperes, divide by 240 volts, and round up to the next standard size. Common residential services are 100, 125, 150 and 200 amps. A typical 1500 square foot all-electric home calculates near 100 amps, while a larger all-electric home often needs 200.
What is the difference between the standard and optional methods?
The standard method in Part III itemizes each load and applies a separate demand factor to each. The optional method in 220.82 groups the general loads and appliances, takes the first 10 kVA at 100% and the remainder at 40%, then adds the largest heating or cooling load. The optional method is simpler and usually gives a lower result for single-family dwellings.
Why is the air conditioner sometimes ignored?
Section 220.60 treats heating and cooling as noncoincident, because a home does not run both at once. Only the larger of the two is included in the calculation. In the default example the 6 kW of electric heat is larger than the 5 kW air conditioner, so the AC drops out entirely.
Does the floor area include the garage?
No. The square footage for the general lighting load excludes open porches, garages, and unused or unfinished spaces that are not adaptable for future use. Use the area of the habitable, conditioned living space only.
Does this use my actual electricity usage?
No. A load calculation sizes the service from rated loads and code demand factors, not from a power bill. The calculated figure is deliberately conservative so the service is never undersized, even though a home rarely draws anywhere near it.
What voltage does the calculator use?
It assumes a 120/240 volt single-phase service, the standard for one-family homes in North America, and divides the total volt-amperes by 240 to get the service amps. It is not set up for 208 volt or three-phase services.
Can I use this for an apartment building or a store?
No. This is a single one-family dwelling calculation. Apartment buildings of three or more units use the demand factors in Table 220.84, and commercial occupancies follow other parts of Article 220. Treat the result here as a rough check only for those cases.
Is this electrical load calculator NEC compliant?
It follows the Article 220 standard method, including the Table 220.42 general demand factors, the Table 220.55 range demand, the 220.54 dryer rule, the 220.53 fixed-appliance factor, and the 220.60 heating and cooling rule. It is an estimating aid for planning, not a substitute for a stamped calculation or a licensed electrician.
The Electrical Cluster & More
The load is the first step. From here, size the conductors, check they fit the conduit, and verify the run length. The full electrical workflow lives here.
Size Your Electrical Service
in 30 Seconds
Enter your home's square footage and major appliances. Get the calculated load in volt-amperes, the service amps, and the panel size you need. All free.
Calculate My Load Takes 30 seconds · No account needed · NEC Article 220