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Dwelling Unit Load Calculations (NEC 220) — NEC 2020 Edition

Free NEC 2020 practice test on dwelling unit load calculations. Covers general lighting loads, small appliance and laundry circuits, demand factors, dryer and appliance loads, and service conductor sizing. Simple English, full explanations.

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This Dwelling Unit Load Calculations (NEC 220) — NEC 2020 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.

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Topics covered: NEC articles 100, 210, 220, 240, 250, 300, 310, 430, and special occupancies.
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Questions: 30 multiple-choice, one correct answer each

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Dwelling Unit Load Calculations (NEC 220) — NEC 2020 Edition — Question List

Question 1: A dwelling unit has 1,600 square feet of living area. Using the NEC general lighting unit load, what is the general lighting load?

4,800 Volt-Amperes
1,600 Volt-Amperes
3,200 Volt-Amperes
6,400 Volt-Amperes

NEC Reference: NEC Table 220.12

Question 2: A quick-recovery electric water heater is rated 5,600 watts at 240 volts. What standard circuit breaker size is required to protect it?

25 amperes
20 amperes
23.3 amperes
30 amperes

NEC Reference: NEC 240.6(A)

Question 3: A dwelling unit has a total connected general lighting and receptacle load of 11,000 VA. What is the calculated demand load?

5,800 VA
11,000 VA
3,850 VA
6,000 VA

NEC Reference: NEC Table 220.42

Question 4: A dwelling unit has an air-conditioning unit with a full-load current of 30 amperes at 230 volts, and 3 fixed heating units of 3 kW each. Since heating and air conditioning will not run at the same time, what load is used for the feeder demand?

9,000 watts
6,900 volt-amperes
15,900 volt-amperes
2,100 watts

NEC Reference: NEC 220.60

Question 5: A dwelling unit has four appliances fastened in place, each rated 800 VA. What is the demand load for these appliances?

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

NEC Reference: NEC 220.53

Question 6: What is the minimum branch-circuit or feeder load that must be used for a single household electric clothes dryer in a dwelling unit?

5,000 Volt-Amperes
1,500 Volt-Amperes
3,000 Volt-Amperes
2,000 Volt-Amperes

NEC Reference: NEC 220.54

Question 7: A multifamily building has 5 household electric clothes dryers, one per dwelling unit. What is the total demand load for these dryers?

21,250 VA
25,000 VA
5,000 VA
18,750 VA

NEC Reference: NEC Table 220.54

Question 8: A 15-unit apartment building has 900 square feet per apartment. What is the total calculated demand load for general lighting, small appliance, and laundry circuits?

39,750 VA
108,000 VA
7,200 VA
75,600 VA

NEC Reference: NEC Table 220.42

Question 9: An 8-unit multifamily building has one 5 kW electric dryer in each unit. What is the total dryer demand load for the building service or feeder?

24 kW
40 kW
20 kW
30 kW

NEC Reference: NEC Table 220.54

Question 10: A 3-phase, 120/230-volt multifamily dwelling building has a total demand load of 220 kVA. Using the standard ampacity method, roughly what current must the service conductors carry?

About 552 amperes
About 220 amperes
About 955 amperes
About 380 amperes

NEC Reference: NEC Table 310.16

Question 11: Each small-appliance branch circuit in a dwelling unit is counted at how many volt-amperes for load calculation purposes?

1,500 VA
1,000 VA
3,000 VA
750 VA

NEC Reference: NEC 220.52(A)

Question 12: The laundry branch circuit in a dwelling unit is counted at how many volt-amperes for load calculation purposes?

1,500 VA
1,000 VA
750 VA
2,000 VA

NEC Reference: NEC 220.52(B)

Question 13: What is the minimum number of small-appliance branch circuits required in a dwelling unit kitchen?

NEC Reference: NEC 210.11(C)(1)

Question 14: A dwelling unit has one household electric range rated 12 kW or less. What demand load is used for the range, per NEC Table 220.55?

8 kW
12 kW
6 kW
10 kW

NEC Reference: NEC Table 220.55

Question 15: For a one-family dwelling, the service disconnecting means must have a rating of not less than what value?

100 amperes
60 amperes
125 amperes
200 amperes

NEC Reference: NEC 230.79(C)

Question 16: For a single-phase dwelling unit service or feeder rated 100 to 400 amperes serving the entire dwelling load, conductors may be sized at not less than what percent of the service or feeder rating?

83%
75%
95%
100%

NEC Reference: NEC 310.12

Question 17: Per NEC Table 220.54, what demand factor applies when there are 4 or fewer household electric clothes dryers?

100%
85%
75%
70%

NEC Reference: NEC Table 220.54

Question 18: For a single dwelling unit, the "optional" load calculation method can be used instead of the standard method under which condition?

Single 120/240V or 208Y/120V service, 100A or more
Only for buildings with 3-phase power
Only for services under 60 amperes
It can never be used for dwellings

NEC Reference: NEC 220.82

Question 19: Using the NEC 220.82 optional dwelling calculation method, what demand factor applies to the first 10 kVA of the "other load" total?

100%
40%
75%
50%

NEC Reference: NEC 220.82(B)

Question 20: Using the NEC 220.82 optional dwelling calculation method, what demand factor applies to the "other load" amount ABOVE the first 10 kVA?

40%
100%
25%
60%

NEC Reference: NEC 220.82(B)

Question 21: A 2,000 square foot dwelling unit has no receptacle or appliance loads beyond the general lighting, small appliance, and laundry circuits. What is the total CONNECTED (before demand factor) load?

10,500 VA
6,000 VA
4,500 VA
13,500 VA

NEC Reference: NEC 220.52

Question 22: Using the 10,500 VA connected load from the previous example, what is the demand load after applying NEC Table 220.42?

5,625 VA
10,500 VA
3,675 VA
3,000 VA

NEC Reference: NEC Table 220.42

Question 23: The NEC 220.53 75% demand factor for fastened-in-place appliances applies starting at how many qualifying appliances?

NEC Reference: NEC 220.53

Question 24: Which of these is EXCLUDED from the NEC 220.53 "four or more fastened appliances" 75% demand factor rule?

Electric range
Dishwasher
Garbage disposal
Water heater

NEC Reference: NEC 220.53

Question 25: A 2,800 square foot dwelling unit is being calculated using the general lighting unit load. What is the connected general lighting load?

8,400 VA
2,800 VA
5,600 VA
9,800 VA

NEC Reference: NEC Table 220.12

Question 26: Per NEC Table 220.54, what demand factor applies to exactly 10 household electric clothes dryers?

NEC Reference: NEC Table 220.54

Question 27: When performing a standard-method dwelling unit load calculation, what is generally done right after finding the general lighting, small-appliance, and laundry connected loads?

Apply the general lighting demand factor
Call the building inspector
Skip straight to the service disconnect size
Ignore the lighting load entirely

NEC Reference: NEC Article 220

Question 28: A duplex (2 dwelling units) has one 5,000 VA electric dryer per unit. What is the total dryer demand load?

10,000 VA
8,500 VA
5,000 VA
9,000 VA

NEC Reference: NEC Table 220.54

Question 29: A single household electric range rated 12 kW or less needs its branch circuit conductors sized for what minimum load, per NEC Table 220.55?

8 kW
12 kW
5 kW
6 kW

NEC Reference: NEC Table 220.55

Question 30: What is the minimum branch-circuit rating required for the small-appliance and laundry circuits in a dwelling unit?

20 amperes
15 amperes
30 amperes
25 amperes

NEC Reference: NEC 210.11(C)

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.

Dwelling Unit Load Calculations (NEC 220) — NEC 2020 Edition

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Dwelling Unit Load Calculations (NEC 220) — NEC 2020 Edition

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Dwelling Unit Load Calculations (NEC 220) — NEC 2020 Edition — Question List

Question 1: A dwelling unit has 1,600 square feet of living area. Using the NEC general lighting unit load, what is the general lighting load?

Question 2: A quick-recovery electric water heater is rated 5,600 watts at 240 volts. What standard circuit breaker size is required to protect it?

Question 3: A dwelling unit has a total connected general lighting and receptacle load of 11,000 VA. What is the calculated demand load?

Question 4: A dwelling unit has an air-conditioning unit with a full-load current of 30 amperes at 230 volts, and 3 fixed heating units of 3 kW each. Since heating and air conditioning will not run at the same time, what load is used for the feeder demand?

Question 5: A dwelling unit has four appliances fastened in place, each rated 800 VA. What is the demand load for these appliances?

Question 6: What is the minimum branch-circuit or feeder load that must be used for a single household electric clothes dryer in a dwelling unit?

Question 7: A multifamily building has 5 household electric clothes dryers, one per dwelling unit. What is the total demand load for these dryers?

Question 8: A 15-unit apartment building has 900 square feet per apartment. What is the total calculated demand load for general lighting, small appliance, and laundry circuits?

Question 9: An 8-unit multifamily building has one 5 kW electric dryer in each unit. What is the total dryer demand load for the building service or feeder?

Question 10: A 3-phase, 120/230-volt multifamily dwelling building has a total demand load of 220 kVA. Using the standard ampacity method, roughly what current must the service conductors carry?

Question 11: Each small-appliance branch circuit in a dwelling unit is counted at how many volt-amperes for load calculation purposes?

Question 12: The laundry branch circuit in a dwelling unit is counted at how many volt-amperes for load calculation purposes?

Question 13: What is the minimum number of small-appliance branch circuits required in a dwelling unit kitchen?

Question 14: A dwelling unit has one household electric range rated 12 kW or less. What demand load is used for the range, per NEC Table 220.55?

Question 15: For a one-family dwelling, the service disconnecting means must have a rating of not less than what value?

Question 16: For a single-phase dwelling unit service or feeder rated 100 to 400 amperes serving the entire dwelling load, conductors may be sized at not less than what percent of the service or feeder rating?

Question 17: Per NEC Table 220.54, what demand factor applies when there are 4 or fewer household electric clothes dryers?

Question 18: For a single dwelling unit, the "optional" load calculation method can be used instead of the standard method under which condition?

Question 19: Using the NEC 220.82 optional dwelling calculation method, what demand factor applies to the first 10 kVA of the "other load" total?

Question 20: Using the NEC 220.82 optional dwelling calculation method, what demand factor applies to the "other load" amount ABOVE the first 10 kVA?

Question 21: A 2,000 square foot dwelling unit has no receptacle or appliance loads beyond the general lighting, small appliance, and laundry circuits. What is the total CONNECTED (before demand factor) load?

Question 22: Using the 10,500 VA connected load from the previous example, what is the demand load after applying NEC Table 220.42?

Question 23: The NEC 220.53 75% demand factor for fastened-in-place appliances applies starting at how many qualifying appliances?

Question 24: Which of these is EXCLUDED from the NEC 220.53 "four or more fastened appliances" 75% demand factor rule?

Question 25: A 2,800 square foot dwelling unit is being calculated using the general lighting unit load. What is the connected general lighting load?

Question 26: Per NEC Table 220.54, what demand factor applies to exactly 10 household electric clothes dryers?

Question 27: When performing a standard-method dwelling unit load calculation, what is generally done right after finding the general lighting, small-appliance, and laundry connected loads?

Question 28: A duplex (2 dwelling units) has one 5,000 VA electric dryer per unit. What is the total dryer demand load?

Question 29: A single household electric range rated 12 kW or less needs its branch circuit conductors sized for what minimum load, per NEC Table 220.55?

Question 30: What is the minimum branch-circuit rating required for the small-appliance and laundry circuits in a dwelling unit?

Key NEC References for This Test

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