Guide to Range Demand Calculation Questions on NEC Electrical Exams (NEC 220.55)

Range (cooking appliance) demand questions are common on NEC-based licensing exams because they test whether you can apply NEC 220.55 and its table notes correctly. In the real world, these calculations help size service/feeder conductors and equipment without oversizing.

This guide shows you exactly how to identify these questions, pick the right Table 220.55 method, and solve them fast.

What the Exam Is Really Testing

Most questions want you to prove you can:

• Recognize a household cooking appliance demand problem (not a general load calc).
• Use Table 220.55 (Column C and/or Notes).
• Apply Note 1 / Note 2 for appliances over 12 kW.
• Use Note 3 when all appliances are 1¾–8¾ kW (or when the question indicates ranges in that band).

How to Spot a Range Demand Question Quickly

Look for these phrases:

• “Household cooking appliances”
• “Range / oven / cooktop”
• “Demand load” or “demand factor”
• “Service entrance conductors” / “feeder”
• Appliance ratings in kW (example: 4.5 kW, 14 kW, 18 kW)
• “Use standard method” (usually implies Table 220.55)

If the question talks about conductor sizing by ampacity, that’s later. First you must find the demand load (kW or VA).

The Core Rule: Use NEC 220.55

Table 220.55 (What You Use Most)

• Column C: Common starting point for many exam problems.
• Notes under the table: This is where most people lose points.

The Big Decision Tree

Use this quick logic:

1. How many cooking appliances? (1, 2, 3…)
2. Are the ratings all in the “small range” band (typically 1¾–8¾ kW)?
   • If yes → Note 3 can apply (often reduces demand).
3. Are any ranges over 12 kW (up to 27 kW)?
   • If yes → you’ll likely use Note 1 (same ratings) or Note 2 (unequal ratings) with Column C.

Formulas You Need (Simple)

Demand Load (kW)

Demand (kW) = Connected Load (kW) × Demand Factor

(Used when Note 3 tells you to apply a demand factor.)

Note 1 (Single appliance over 12 kW through 27 kW, or all equal)

Increase the Column C demand by:

• 5% for each kW (or major fraction) over 12 kW

Note 2 (Multiple appliances over 12 kW through 27 kW, unequal ratings)

1. Find average rating Average (kW) = Total Connected (kW) ÷ Number of appliances
2. Increase Column C demand by: 5% per kW (or major fraction) above 12 kW based on the average

Walkthrough Examples (Exam Style)

Example 1 — Mixed Ratings in the Note 3 Range

Question: A dwelling has two ranges rated 4.5 kW each and one range rated 7 kW. Find the demand load on the ungrounded service entrance conductors.

Step 1: Total connected load

4.5 + 4.5 + 7 = 16 kW

Step 2: Identify the situation

All three are between 3½–8¾ kW, so Note 3 can apply.

Step 3: Use Note 3 demand factor (Column B)

For 3 appliances and 16 kW total, the demand factor is 55% (as in your example set).

Step 4: Demand load

16 kW × 0.55 = 8.8 kW

✅ Answer: 8.8 kW

Exam tip: Always compare with Column C maximum demand. If Note 3 gives a smaller value, use it when permitted.

Example 2 — One Range Over 12 kW (Use Note 1)

Question: One household range rated 15 kW. Find the demand load.

Step 1: Start from Column C

For 1 appliance, Column C base demand is 8 kW (common exam assumption).

Step 2: Apply Note 1 adjustment

15 kW is 3 kW over 12 kW

Increase = 3 × 5% = 15%

Step 3: Increase the base demand

8 kW × 1.15 = 9.2 kW

✅ Answer: 9.2 kW

Common mistake: People increase the connected load. Note 1 increases the Column C demand, not the nameplate kW.

Example 3 — Two Ranges Over 12 kW (Unequal → Note 2)

Question: Two ranges: 14 kW and 18 kW. Find the demand load.

Step 1: Total connected load

14 + 18 = 32 kW

Step 2: Average rating (Note 2)

32 ÷ 2 = 16 kW average

Step 3: Determine increase above 12 kW

16 − 12 = 4 kW

Increase = 4 × 5% = 20%

Step 4: Start with Column C demand for 2 appliances

Base demand (Column C for 2 appliances) = 11 kW (common exam value)

Step 5: Apply the increase

11 kW × 1.20 = 13.2 kW

✅ Answer: 13.2 kW

Fast Checklist (Use This During the Exam)

Before you calculate anything, confirm:

• ✅ Is it household cooking appliances?
• ✅ How many appliances?
• ✅ Are they all ≤ 8¾ kW (Note 3 territory)?
• ✅ Any appliance > 12 kW and ≤ 27 kW (Note 1/2 territory)?
• ✅ Does the question ask for demand load (kW/VA) vs conductor size (amps)?

Common Pitfalls (What Costs Points)

• Using ampacity rules when the problem is purely demand.
• Forgetting to check Note 3 for smaller ranges (and missing an easier answer).
• Applying the 5% increase to connected load instead of Column C demand.
• Not using average rating for unequal >12 kW ranges (Note 2).
• Mixing up “demand” vs “nameplate” values.

Quick Practice Tip

If you’re building speed:

• Memorize the flow (Note 3 vs Note 1/2).
• Get comfortable with percent increases (5% per kW over 12).
• Always write the demand in kW first, then convert to amps only if asked.

FAQ

Is voltage drop part of range demand questions?

No. Range demand is NEC 220.55. Voltage drop is a different topic.

Do I always use Column C?

Column C is often the starting point, but Note 3 can override for smaller ranges, and Notes 1/2 modify Column C for larger ranges.

Do I need to size the neutral here?

Only if the question specifically asks. Neutral sizing is typically a different exam question set.