Electrical Load Calculator for Homes

See if your panel can handle an EV charger, heat pump, or hot tub

Project Details
Enter your measurements and requirements

The number printed on the large breaker at the top of the panel.

Planned additions

11,520W
7,680W
4,500W
6,000W
6,000W
18,000W
3,000W
6,000W

Used to calculate general lighting load (3 VA/sq ft per NEC 220.12)

Kitchen/dining (1500 VA each)

1500 VA each

Appliances & Equipment

12,000W
6,000W
5,000W
1,500W
1,800W
900W
700W
500W

3,500W
4,500W
5,500W
3,500W
4,500W
15,000W
1,500W

Or enter exact nameplate ratings:

Results
Calculated estimates for your project

Your 100 A panel

Fits with load management (EVEMS, NEC 625.42)

19 A over (119 A calculated on a 100 A service). Panel used: 100% today, 119% after.

An EV load management device caps the charger when the house is busy, usually $400 to $1,000 instead of an upgrade.

Standard Method

167 A

200 A service

Optional Method (220.82)

119 A

125 A service

Total Load

40,020 VA

Total Amperage

166.8 A

Recommended Service Size

200 A

83% of service capacity used

Load worksheet (Standard Method)

General lighting and receptacles, 3 VA per sq ft (220.12)6,000 VA
Small appliance circuits, 1,500 VA each (220.52(A))3,000 VA
Laundry circuit, 1,500 VA each (220.52(B))1,500 VA
Demand adjustment on the three lines above (Table 220.42)-4,875 VA
Cooking equipment (220.55)8,000 VA
Electric dryer, 5,000 VA minimum (220.54)5,000 VA
Fixed appliances at 75% (4 or more) (220.53)6,375 VA
Larger of heating or cooling (220.60)3,500 VA
EV charging at 100% (continuous) (625.42)11,520 VA
Total, divided by 240 V166.8 A

Note: This is an estimate based on NEC Article 220. Actual requirements may vary. Always consult a licensed electrician for service upgrades and permit requirements.

Turn these numbers into a build plan.

  • 100 A panel
  • 119 A (119%) load after additions
  • Fits with load management verdict

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Add EV Charger Level 2 with load management on a 100 A panel

The house calculates to 100 A today and 119 A with EV Charger Level 2, on a 100 A service (119% used). An energy management system can cap the EV charger so the panel never overloads, which avoids an upgrade. A licensed electrician does the panel work; this plan keeps the quotes, permit and utility steps in order.

Materials
$1,500
Time
1 to 2 weeks
Level
Advanced
7 steps 3 tools 4 materials
  1. 1

    Confirm the panel and the load sheet

    Check the main breaker reads 100 A and save the itemized load calculation. Note the panel brand and open breaker slots.

    • Photo of the main breaker
    • Photo of the panel label
    • Count open slots
  2. 2

    Get three electrician quotes

    Send each electrician the worksheet and photos so the quotes compare the same scope.

    • Licensed and insured
    • Permit included in the price
    • Itemized breaker and wire sizes
  3. 3

    Pull the permit

    Most jurisdictions need a permit for a new 240 V circuit. Your electrician usually pulls it.

01 · Your numbers
Panel
100 A
Load after additions
119 A (119%)
Verdict
Fits with load management
02 · The plan

7 steps · 3 tools · 4 materials

4 more steps, the full tool list and a shopping list you can check off as you go.

03 · Finished

Your plan is 60% built. Save it.

3/5

Add EV Charger Level 2 with load management on a 100 A panel

Finished in 1 to 2 weeks · $1,500 DIY

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Worked example: 2,000 sq ft house adding a 48 A EV charger

Electric range, dryer, 50 gallon water heater, 3 ton central A/C, dishwasher, disposal and fridge, then a Level 2 charger on a 48 A circuit.

  1. General lighting and receptacles, 3 VA per sq ft (NEC 220.12). 6,000 VA for the 2,000 sq ft example house with a 48 A EV charger.
  2. Small appliance circuits, 1,500 VA each (NEC 220.52(A)). 3,000 VA for the 2,000 sq ft example house with a 48 A EV charger.
  3. Laundry circuit, 1,500 VA each (NEC 220.52(B)). 1,500 VA for the 2,000 sq ft example house with a 48 A EV charger.
  4. Demand adjustment on the three lines above (NEC Table 220.42). -4,875 VA for the 2,000 sq ft example house with a 48 A EV charger.
  5. Cooking equipment (NEC 220.55). 8,000 VA for the 2,000 sq ft example house with a 48 A EV charger.
  6. Electric dryer, 5,000 VA minimum (NEC 220.54). 5,000 VA for the 2,000 sq ft example house with a 48 A EV charger.
  7. Fixed appliances at 75% (4 or more) (NEC 220.53). 7,050 VA for the 2,000 sq ft example house with a 48 A EV charger.
  8. Larger of heating or cooling (NEC 220.60). 3,500 VA for the 2,000 sq ft example house with a 48 A EV charger.
  9. EV charging at 100% (continuous) (NEC 625.42). 11,520 VA for the 2,000 sq ft example house with a 48 A EV charger.
  10. Divide by 240 volts. 40,695 VA / 240 V = 170 A, so the house needs at least a 200 A service.

The Optional Method gives 28,868 VA, or 120 A. On a 100 A panel the lower of the two is 120 A; on a 200 A panel it leaves 80 A spare.

Standard vs Optional method

Standard (220.40)Optional (220.82)
Lighting and receptacles3 VA per sq ft, demand factored3 VA per sq ft
Small appliance and laundry1,500 VA each, demand factored1,500 VA each
Range8 kW for one up to 12 kWNameplate
Dryer5,000 VA or nameplateNameplate
Everything aboveSeparate factors per lineFirst 10 kVA at 100%, rest at 40%
Heating and coolingLarger of the two at 100%Largest of A/C, heat pump plus 65% strip, or 65% space heat
Example result170 A120 A

The optional method is allowed for any single dwelling served by one 120/240 V service, and for an existing house NEC 220.83 has a similar version. Use whichever your inspector accepts; most permit worksheets follow 220.82.

How to read your panel's main breaker

The service size is the number on the largest breaker, usually at the top of the panel and often labeled MAIN. It can also be on the panel label inside the door. If there is no main breaker, the service may be limited by the meter base or the wire from the utility; an electrician can confirm. The sum of all the branch breakers does not matter: a 100 A panel with 160 A of breakers is normal.

What uses the most load

ApplianceWattsAmps at 240 V
Electric Range/Oven12,00050
Electric Dryer5,00021
Water Heater (50 gal)5,50023
Tankless Water Heater18,00075
Central A/C (4 ton)4,50019
Heat Pump (4 ton)4,50019
Electric Furnace15,00063
EV Charger Level 2 (32A)7,68032
EV Charger Level 2 (48A)11,52048
Hot Tub/Spa6,00025
Pool Heater (Electric)11,00046

The 80% continuous-load rule

A load that runs three hours or more, like an EV charger, may use only 80% of its breaker. A 48 A charger needs a 60 A breaker and a 40 A charger a 50 A breaker. That is a branch circuit rule; the service calculation already counts EV charging at 100%.

Load management instead of an upgrade

An energy management system (NEC 220.70 and 625.42) watches the main feed and throttles or pauses the charger when the house is busy. Many chargers have it built in, and add-on units run $400 to $1,000. Smart panels and circuit pausers do the same for a water heater or hot tub.

Service upgrade cost

UpgradeTypical installed cost
100 A to 200 A$2,000 to $4,500
200 A to 400 A (320 A meter)$4,000 to $9,000
Load management device$400 to $1,000

When you need a permit

A service upgrade always needs a permit and a utility disconnect. Most places also want one for a new 240 V circuit such as an EV charger, hot tub or heat pump. Bring the printed worksheet; check the circuit length with the voltage drop calculator, and see the EV charger installation cheat sheet and the NEMA plug chart. To offset the new load, run the solar calculator; an electric tankless heater is sized in the tankless water heater calculator.

Electrical load calculator FAQ

Can a 100 amp panel handle an EV charger?

Sometimes. In our example 2,000 sq ft house with an electric range, dryer, water heater and central A/C, a 48 A Level 2 charger pushes the load to 120 A on a 100 A service: too much on paper, but an EV load management device (NEC 625.42) can make it work. A 32 A charger, a gas range or dryer, or a load management device often avoids the upgrade.

How many amps does a house use?

A typical 2,000 sq ft house calculates to 80 to 120 A with electric cooking, drying and A/C, and 50 to 80 A with gas appliances. Actual draw most of the day is far lower; the load calculation sizes the service for the busiest hour.

What is the difference between the standard and optional load calculation?

The Standard Method (NEC 220.40) applies separate demand factors to lighting, cooking, dryers and fixed appliances. The Optional Method (220.82) adds every general load at nameplate, counts the first 10 kVA at 100% and the rest at 40%, then adds the largest heating or cooling load. The optional method usually gives a lower answer for a single-family house and is what most permit worksheets use.

What is a NEC load calculation worksheet?

The line-by-line form a building department asks for with a service upgrade or large new circuit. It lists each load, the code section and the volt-amps, then divides the total by 240 V. The worksheet on this page follows the same order and prints on one page.

Can I run a heat pump and an EV charger on 200 amps?

Usually yes. A 4 ton heat pump with 10 kW of strip heat and a 48 A charger on a 2,000 sq ft house calculates well under 200 A with the optional method. Very large houses, electric tankless water heaters or a second EV can push it past 200 A.

Why doesn't the calculator just add up all watts?

Not everything runs at once. The NEC demand factors reflect that: lighting and receptacles drop to 35% past the first 3,000 VA, a 12 kW range counts as 8 kW, and only the larger of heating or cooling is counted.

How much does a service upgrade cost?

About $2,000 to $4,500 for 100 A to 200 A, and $4,000 to $9,000 for 200 A to 400 A, including the panel, meter base and permit. A new utility drop or a trench adds to that.

What's the difference between VA and watts?

VA (volt-amps) is apparent power and watts is real power. For household loads they are close to equal, and the NEC uses VA for load calculations.

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