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Single-Family Dwelling Load Calculations (NEC 220) — NEC 2023 Edition

Free NEC 2023 practice test on single-family dwelling load calculations. Covers general lighting loads, appliance and dryer demand factors, service conductor sizing, and bathroom GFCI protection. Simple English, full explanations.

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The National Electrical Code (NFPA 70) is the benchmark standard for safe electrical installation in the US. It is updated every 3 years by the NFPA.

Study the edition adopted by your state. As of 2025, most states use the 2020 or 2023 NEC. These tests are written to the 2023 edition.

The most tested articles are 100 (Definitions), 200–250 (Wiring & Grounding), 300–314 (Wiring Methods), 400–411 (Conductors), 430 (Motors), and 700–701 (Emergency Systems).

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This Single-Family Dwelling Load Calculations (NEC 220) — NEC 2023 Edition has 30 questions with detailed answers and NEC references. Take the full test, review every wrong answer, and look up the NEC article it references before moving on.

Tip: Use the NEC index (back of the book) — find answers by keyword, not by article number.

Topics covered: NEC articles 100, 210, 220, 240, 250, 300, 310, 430, and special occupancies.
Passing score: Aim for 80%+ on NEC code tests before exam day.
Questions: 30 multiple-choice, one correct answer each

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Single-Family Dwelling Load Calculations (NEC 220) — NEC 2023 Edition — Question List

Question 1: What is the minimum feeder or service load that must be used for a household electric clothes dryer in a dwelling unit?

5,000 watts
2,500 watts
4,000 watts
6,500 watts

NEC Reference: NEC 220.54

Question 2: A single-family unit has one air conditioner rated 3 kW and fixed heating equipment rated 2.5 kW. Since these will not run at the same time, what is the total calculated load for both?

3 kW
2.5 kW
5.5 kW
1.5 kW

NEC Reference: NEC 220.60

Question 3: Service or feeder conductors that supply the entire load of one dwelling unit may be sized at not less than what percent of the service or feeder rating?

NEC Reference: NEC 310.12

Question 4: What is the general lighting unit load, used for branch-circuit and feeder/service calculations, for a single-family dwelling unit?

3 Volt-amperes per square foot
2 Volt-amperes per square foot
1 Volt-ampere per square foot
4 Volt-amperes per square foot

NEC Reference: NEC Table 220.42

Question 5: In a single-family dwelling unit, when four or more appliances are fastened in place and connected to the same feeder, what demand factor can be applied to their total load?

NEC Reference: NEC 220.53

Question 6: What is the minimum general lighting load required for a 1,500 square foot single-family house?

4,500 VA
4,800 VA
3,000 VA
1,500 VA

NEC Reference: NEC Table 220.42

Question 7: On a 15-ampere branch circuit supplying fixed lighting units in a dwelling unit, what type of lampholder is required?

Standard-duty lampholders
Heavy-duty lampholders
Explosion-proof lampholders
No lampholder is permitted

NEC Reference: NEC 210.23

Question 8: All 15- and 20-ampere, 125-volt receptacle outlets installed in dwelling unit bathrooms must always have what protection?

Non-grounding receptacles
Weatherproof receptacles
Ground-fault circuit-interrupter (GFCI) protection
A protective guard only

NEC Reference: NEC 210.8(A)(1)

Question 9: For a single-family dwelling unit, what is the minimum allowable rating of a 3-wire, 120/240-volt service disconnecting means?

125 amperes
100 amperes
150 amperes
175 amperes

NEC Reference: NEC 230.79(C)

Question 10: What protection is required for 125-volt, 15- and 20-ampere receptacles serving dwelling unit kitchen countertop surfaces?

GFCI protection
No protection is required
AFCI protection only
A dedicated 50-ampere circuit

NEC Reference: NEC 210.8(A)(6)

Question 11: In a single-family dwelling, which 125-volt, 15- and 20-ampere receptacles must be tamper-resistant?

Essentially all dwelling unit receptacles
Only rooms with small children
Only outdoor receptacles
Only garage receptacles

NEC Reference: NEC 406.12

Question 12: In dwelling unit habitable rooms, receptacles must be placed so no point along the floor line is more than how far from a receptacle outlet?

6 feet
4 feet
8 feet
10 feet

NEC Reference: NEC 210.52(A)(1)

Question 13: In a single-family dwelling unit, 120-volt, 15- and 20-ampere branch circuits supplying outlets in habitable rooms generally require what protection?

AFCI protection
No protection is required
GFCI protection only
A padlock on the panel

NEC Reference: NEC 210.12(A)

Question 14: A single-family dwelling service uses 2 AWG copper ungrounded conductors. What is the minimum size copper grounding electrode conductor required?

8 AWG
10 AWG
6 AWG
4 AWG

NEC Reference: NEC Table 250.66

Question 15: Central heating equipment in a single-family dwelling must generally be supplied by what type of circuit?

An individual branch circuit
The kitchen small-appliance circuit
Any lighting circuit
A shared water heater circuit

NEC Reference: NEC 210.11(C)(4)

Question 16: A single-family home has one household electric range rated 12 kW or less. Per NEC Table 220.55, what demand load is used?

8 kW
12 kW
6 kW
10 kW

NEC Reference: NEC Table 220.55

Question 17: For a one-family dwelling, at least one receptacle outlet must be installed where, in addition to indoor rooms?

Outdoors, front and back of the dwelling
Only in the attic
Only in a locked shed
None is required outdoors

NEC Reference: NEC 210.52(E)(1)

Question 18: What is the additional branch circuit rating required for dwelling unit bathroom receptacle outlets?

20 amperes
15 amperes
25 amperes
10 amperes

NEC Reference: NEC 210.11(C)(3)

Question 19: A single-family dwelling has a metal underground water pipe in direct contact with earth for at least 10 feet. What must be done with it?

Used as a grounding electrode, with a supplemental electrode
Ignored completely
Removed from the ground
Painted for identification only

NEC Reference: NEC 250.52(A)(1)

Question 20: The dwelling unit laundry branch circuit must supply only laundry receptacle outlets, and must not supply what?

Lighting outlets in another room
More laundry receptacles
The washing machine
A single laundry room light

NEC Reference: NEC 210.11(C)(2)

Question 21: A single-family dwelling has a single 120/240-volt service rated 150 amperes. Which optional load calculation method could be used instead of the standard method?

The NEC 220.82 optional method
No optional method is ever allowed
A method only for 3-phase services
A method requiring a 60-amp service

NEC Reference: NEC 220.82

Question 22: A single-family dwelling has 5 fastened-in-place appliances (not ranges, dryers, or HVAC equipment), each rated 1,000 VA. What is the appliance demand load?

3,750 VA
5,000 VA
2,500 VA
4,250 VA

NEC Reference: NEC 220.53

Question 23: In a single-family dwelling service, what connects the equipment grounding conductor to the grounded (neutral) conductor at the service?

The main bonding jumper
A telephone ground wire
Nothing is required
A gas pipe only

NEC Reference: NEC 250.28

Question 24: A 1,200 square foot single-family dwelling is being calculated using the general lighting unit load. What is the connected load?

3,600 VA
1,200 VA
2,400 VA
4,800 VA

NEC Reference: NEC Table 220.42

Question 25: A single-family dwelling uses two ground rods as part of its grounding electrode system. How far apart should they be spaced, at minimum?

6 feet
1 foot
50 feet
Touching each other

NEC Reference: NEC 250.53(A)(3)

Question 26: For the electrical panel in a single-family dwelling, what is the minimum required clear working space depth in front of it, under normal (Condition 2) conditions at typical residential voltage?

3 feet
1 foot
6 feet
10 feet

NEC Reference: NEC Table 110.26(A)(1)

Question 27: Dwelling unit smoke alarms that are hardwired must generally be connected to a circuit that is NOT protected by which of the following?

A switch that can turn off the alarm circuit
A regular breaker
A metal box
A neutral conductor

NEC Reference: NFPA 72 / NEC 210.12

Question 28: A service mast used to support the service-drop conductors on a single-family dwelling must be able to do what?

Withstand the strain, with adequate strength or bracing
Bend freely in the wind
Be left unsupported
Be removed after installation

NEC Reference: NEC 230.28

Question 29: When sizing service equipment for a single-family dwelling that already has, or is adding, electric vehicle charging equipment, the EVSE load must be treated as what?

A continuous load
A load that is always ignored
A momentary load only
A load that cancels out the range load

NEC Reference: NEC 625.41

Question 30: A dwelling unit's panelboard circuit directory must identify each circuit's purpose. Where must this directory be located?

On the face or inside of the panel door
In a filing cabinet elsewhere
Nowhere -- it is optional
Only in the electrician's notebook

NEC Reference: NEC 408.4(A)

Key NEC References for This Test

Article	What It Covers
Ch. 1–4	General rules — apply to all installations
Ch. 5–7	Special rules — override Ch. 1–4 where they conflict
Ch. 8	Communications — completely independent of Ch. 1–7
Ch. 9	Tables — referenced by articles, not standalone enforceable rules
Art. 210.12	AFCI — major expansion in NEC 2026
Art. 230.67	Surge protection at service equipment — new NEC 2026

Study Tip: Learn the NEC index — use keywords, not article numbers. Practice finding 5 different topics in under 2 minutes each.

Single-Family Dwelling Load Calculations (NEC 220) — NEC 2023 Edition

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Key NEC References for This Test

Single-Family Dwelling Load Calculations (NEC 220) — NEC 2023 Edition

How this test works

Frequently Asked Questions

Is this Single-Family Dwelling Load Calculations (NEC 220) — NEC 2023 Edition free?

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How to Use This Practice Test

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Single-Family Dwelling Load Calculations (NEC 220) — NEC 2023 Edition — Question List

Question 1: What is the minimum feeder or service load that must be used for a household electric clothes dryer in a dwelling unit?

Question 2: A single-family unit has one air conditioner rated 3 kW and fixed heating equipment rated 2.5 kW. Since these will not run at the same time, what is the total calculated load for both?

Question 3: Service or feeder conductors that supply the entire load of one dwelling unit may be sized at not less than what percent of the service or feeder rating?

Question 4: What is the general lighting unit load, used for branch-circuit and feeder/service calculations, for a single-family dwelling unit?

Question 5: In a single-family dwelling unit, when four or more appliances are fastened in place and connected to the same feeder, what demand factor can be applied to their total load?

Question 6: What is the minimum general lighting load required for a 1,500 square foot single-family house?

Question 7: On a 15-ampere branch circuit supplying fixed lighting units in a dwelling unit, what type of lampholder is required?

Question 8: All 15- and 20-ampere, 125-volt receptacle outlets installed in dwelling unit bathrooms must always have what protection?

Question 9: For a single-family dwelling unit, what is the minimum allowable rating of a 3-wire, 120/240-volt service disconnecting means?

Question 10: What protection is required for 125-volt, 15- and 20-ampere receptacles serving dwelling unit kitchen countertop surfaces?

Question 11: In a single-family dwelling, which 125-volt, 15- and 20-ampere receptacles must be tamper-resistant?

Question 12: In dwelling unit habitable rooms, receptacles must be placed so no point along the floor line is more than how far from a receptacle outlet?

Question 13: In a single-family dwelling unit, 120-volt, 15- and 20-ampere branch circuits supplying outlets in habitable rooms generally require what protection?

Question 14: A single-family dwelling service uses 2 AWG copper ungrounded conductors. What is the minimum size copper grounding electrode conductor required?

Question 15: Central heating equipment in a single-family dwelling must generally be supplied by what type of circuit?

Question 16: A single-family home has one household electric range rated 12 kW or less. Per NEC Table 220.55, what demand load is used?

Question 17: For a one-family dwelling, at least one receptacle outlet must be installed where, in addition to indoor rooms?

Question 18: What is the additional branch circuit rating required for dwelling unit bathroom receptacle outlets?

Question 19: A single-family dwelling has a metal underground water pipe in direct contact with earth for at least 10 feet. What must be done with it?

Question 20: The dwelling unit laundry branch circuit must supply only laundry receptacle outlets, and must not supply what?

Question 21: A single-family dwelling has a single 120/240-volt service rated 150 amperes. Which optional load calculation method could be used instead of the standard method?

Question 22: A single-family dwelling has 5 fastened-in-place appliances (not ranges, dryers, or HVAC equipment), each rated 1,000 VA. What is the appliance demand load?

Question 23: In a single-family dwelling service, what connects the equipment grounding conductor to the grounded (neutral) conductor at the service?

Question 24: A 1,200 square foot single-family dwelling is being calculated using the general lighting unit load. What is the connected load?

Question 25: A single-family dwelling uses two ground rods as part of its grounding electrode system. How far apart should they be spaced, at minimum?

Question 26: For the electrical panel in a single-family dwelling, what is the minimum required clear working space depth in front of it, under normal (Condition 2) conditions at typical residential voltage?

Question 27: Dwelling unit smoke alarms that are hardwired must generally be connected to a circuit that is NOT protected by which of the following?

Question 28: A service mast used to support the service-drop conductors on a single-family dwelling must be able to do what?

Question 29: When sizing service equipment for a single-family dwelling that already has, or is adding, electric vehicle charging equipment, the EVSE load must be treated as what?

Question 30: A dwelling unit's panelboard circuit directory must identify each circuit's purpose. Where must this directory be located?

Key NEC References for This Test

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