Calculator | Electrical Load

Electrical load calculator.

Calculate a dwelling service load in the order the exam expects: square footage, required circuits, demand factor, range, dryer, water heater, larger of heat or AC, EVSE, then service size.

Built for residential dwelling load questions. Commercial load studies and engineering design need a different workflow.

Direct answer: for a dwelling electrical load calculation, start with 3 VA per square foot, add the required small-appliance and laundry circuits, apply the dwelling demand factor, add large appliances, use the larger of heat or AC, then divide total VA by service voltage.

Square footage of dwelling

Small appliance circuits (min 2)Laundry circuits (min 1)

Range nameplate (W)0 if no range. Single household range. Demand from Table 220.55 column C.Dryer nameplate (W)0 if no dryer. NEC enforces a 5,000 W minimum if present.Water heater (W)0 if none.Electric heat (W)Resistance heat or strip heat at full output.Air conditioning (tons)1 ton ≈ 3,600 VA. Larger of heat or AC will be used.EVSE charging current (A)0 if none. Continuous load. Gets a 125% multiplier.

Total demand load37045 VA

Service current (240 V)154.35 A

Conductor sizing (83% rule)166.00 A

Recommended service200 A

A 200A service is the next standard rating for this calculated load. The conductor number applies the 83% dwelling-service allowance where that rule qualifies.

Drill dwelling load questions

Worked example

2,400 sq ft dwelling with range, dryer, heat, and AC

Inputs

2,400 sq ft dwelling
Two small-appliance circuits and one laundry circuit
12 kW range and 5 kW dryer
15 kW heat
5 ton AC

Result

General-load demand is 6,045 VA. Add range, dryer, and the larger of heat or AC. With the calculator convention of 3,600 VA per AC ton, the total is 37,045 VA, or about 154 A at 240 V. That rounds to a 200 A service.

Here is the trap: do not add heat and AC together. Pick the larger one and move on. That one mistake can push the answer into the next service size.

Common misses

Electrical load mistakes that cost exam points

Skipping required circuits. Two small-appliance circuits and one laundry circuit belong in the general dwelling load before the demand factor.
Adding heat and AC. They are noncoincident for this calculation. Use the larger one.
Using the dryer nameplate when it is too low. If a dryer is present, the minimum is 5,000 VA.
Applying 83% too early. Pick the dwelling service rating first, then apply the conductor allowance to the selected rating.

Related practice

After the load calculation, drill the setup

Dwelling load calculatorThe same calculator under the NEC Article 220 naming.NEC 220 dwelling load guideWalk the Article 220 setup without relying on the calculator.California dwelling load practiceCalifornia General Electrician load calculation drills.Take the free diagnosticFind out whether load calculation is one of your weak areas.

FAQ

Electrical load calculator questions

What kind of electrical load does this calculator handle?

This page handles the standard dwelling service-load setup used on many electrician exams. It is built around Article 220 dwelling load steps, not commercial load studies.

Do I add heat and air conditioning together?

No. For this dwelling calculation, heat and AC are treated as noncoincident loads. Use the larger value and leave out the smaller one.

What loads are included?

The calculator includes general lighting, small-appliance circuits, laundry circuit, range, dryer, water heater, larger of heat or AC, EVSE, and the 310.12 dwelling service-conductor allowance.

Is this the same as a commercial electrical load calculation?

No. Commercial service and feeder calculations use different assumptions. Use this page for dwelling exam practice and residential service-load checks.

Why does the calculator show service conductor amps?

After the dwelling service rating is selected, qualifying dwelling service conductors can use the 83% allowance. That step is a common exam trap.

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