This guide details NEC 220.52 calculations for small appliance and laundry load sizing accurately today.
Engineers and electricians will learn circuit amperage, demand factors, feeder sizing, and verification procedures practically.
NEC 220.52 Small Appliance and Laundry Load Calculator (Circuit Sizing in Amperes)
Regulatory framework and scope for NEC 220.52 calculations
NEC Article 220 establishes methods for calculating loads in dwelling occupancies. Article 220.52 specifically addresses small-appliance and laundry loads for dwelling units, defining a standardized VA allocation used for demand-load computations. Independent branch-circuit requirements appear in Article 210 (for example, small-appliance branch circuits and laundry branch circuits), which mandate minimum numbers and overcurrent ratings. This article explains how to convert NEC prescribed VA values into branch-circuit and feeder amperages and provides practical calculators and worked examples. Key regulatory points to consider:- NEC 220.52 — prescribed VA for small-appliance and laundry loads (per dwelling unit).
- NEC 210.11 and 210.52 — minimum branch-circuit count and location of receptacles in dwelling units.
- NEC 310 and 240 — conductor ampacity and overcurrent protection device selection rules.
- Local amendments or edition year differences (2017, 2020, 2023) may change text; always verify the adopted edition.
- NFPA 70 (NEC) overview: https://www.nfpa.org/NEC
- NEC text references (purchase/lookup): https://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards
- Practical compliance guidance from IAEI: https://www.iaei.org
Fundamental approach: from VA to amps to circuit sizing
NEC 220.52 prescribes VA allocations that are converted to currents using the basic power equation. Use these steps to size circuits instantly:- Identify the number of required small-appliance branch circuits (minimum two per dwelling unit per NEC).
- Assign the standard VA per circuit (per NEC 220.52) for small-appliance and laundry loads.
- Sum applicable loads and convert total VA to amperes using the applicable system voltage.
- Apply demand factors only where permitted by NEC (many small-appliance calculations are fixed per-circuit VA values without additional demand multipliers).
- Select conductors and overcurrent protective devices per NEC 310 and 240 using ampacity adjustment rules, temperature ratings, and terminal limitations.
Basic electrical formula used
Formula: I = P / V
Where:
- I = current in amperes (A)
- P = power in volt-amperes (VA) or watts (W) (NEC allocations are in VA)
- V = voltage in volts (V) — typically 120 V for small-appliance and laundry branch circuits in dwellings
- P (small-appliance branch circuit) = 1,500 VA per circuit (NEC 220.52 standard allocation)
- P (laundry) = 1,500 VA (NEC allocated value for laundry load)
- V = 120 V for receptacle branch circuits
NEC-prescribed VA allocations and typical conversions
NEC requires that small-appliance branch circuits be calculated using specified VA values rather than actual measured loads. The standardized allocation simplifies compliance and helps ensure adequate service sizing across dwellings.| NEC Item | Allocated VA | Typical Voltage | Calculated Current (I = P / V) | Typical Overcurrent Device |
|---|---|---|---|---|
| Small-appliance branch circuit (per circuit) | 1,500 VA | 120 V | 12.5 A | 20 A breaker (minimum per NEC for circuit) |
| Laundry (allocated) | 1,500 VA | 120 V | 12.5 A | 20 A laundry branch circuit (min per NEC) |
| Minimum required small-appliance branch circuits per dwelling | 2 circuits × 1,500 VA = 3,000 VA | 120 V | 25 A (total, not individual) | Two 20 A breakers |
| Example total small-appliance + laundry allocation | 3,000 VA + 1,500 VA = 4,500 VA | 120 V | 37.5 A (service calculation basis) | Feeder sizing per NEC 220 |
- Although 1,500 VA converts to 12.5 A at 120 V, NEC requires small-appliance and laundry branch circuits to be at least 20 A, thus the branch-circuit breaker rating is 20 A even though calculated load is 12.5 A per circuit.
- For service- and feeder-load calculations, NEC uses the sum of allocated VA values and applies further demand adjustments per other parts of Article 220.
Detailed formula set and variable explanations
Provide formulas you can use programmatically or in spreadsheet calculators. All formulas are shown in plain HTML.Formula for branch-circuit current from NEC allocation:
I_branch = P_alloc / V_system
Where:
- I_branch = calculated current per circuit (A)
- P_alloc = allocated power in VA (NEC 220.52 uses 1,500 VA for small-appliance and laundry)
- V_system = line voltage in volts (typically 120 V for these circuits)
Formula for total allocated load used in service/feeder calculation:
P_total = N_sabc × 1,500 + P_laundry + other_allocations
Where:
- P_total = total allocated VA for small appliance and laundry
- N_sabc = number of small-appliance branch circuits (minimum 2 per dwelling; additional circuits may be required by local appliance counts)
- P_laundry = laundry allocation (1,500 VA as per NEC allocation)
Convert total VA to feeder current:
I_feeder = P_total / V_phase
Where V_phase = 120 V (for single-phase neutral loads) or 240 V where appropriate for combined calculations depending on how loads are split across phases; consult NEC for feeder calculation method and conductor sizing rules.
Examples of typical parameter values:- N_sabc = 2 (minimum)
- P_alloc (per small-appliance circuit) = 1,500 VA
- P_laundry = 1,500 VA
- V_system = 120 V (for receptacle circuits) or 240 V for combined feeder distribution when calculating total service current — see worked examples below.
Tables of common computed values for quick reference
Use these lookup values for instant sizing and calculator design.| Number of Small-Appliance Circuits (N) | Small-Appliance VA (N × 1,500 VA) | + Laundry VA (if included) | Total VA | Equivalent Current @120 V | Suggested minimum breakers |
|---|---|---|---|---|---|
| 2 | 3,000 VA | +0 VA | 3,000 VA | 25.0 A | Two 20 A circuits |
| 2 | 3,000 VA | +1,500 VA | 4,500 VA | 37.5 A | Two 20 A circuits + one 20 A laundry |
| 3 | 4,500 VA | +1,500 VA | 6,000 VA | 50.0 A | Three 20 A circuits + one 20 A laundry |
| 4 | 6,000 VA | +1,500 VA | 7,500 VA | 62.5 A | Four 20 A circuits + one 20 A laundry |
| Common Conductor Size (Copper) | Typical Max Breaker (ampere) | NEC Common Usage |
|---|---|---|
| 14 AWG | 15 A | Lighting and small loads (not used for small-appliance circuits) |
| 12 AWG | 20 A | Small-appliance and laundry branch circuits (NEC requires 20A) |
| 10 AWG | 30 A | General-purpose branch circuits and small loads requiring 30A |
| 8 AWG | 50 A | Ranges and large loads (breakers commonly 40–50 A depending on appliance) |
| 6 AWG | 65 A | Service and feeder applications for moderate loads |
Practical calculator algorithm (step-by-step)
Algorithm suitable for spreadsheet or embedded script:- Input number of dwelling units, N_units.
- For each unit, set N_sabc = max(2, user_defined_small_appliance_circuits).
- Compute P_sabc_total = N_units × N_sabc × 1,500.
- Compute P_laundry_total = N_units × 1,500 (if laundry circuit required per dwelling).
- Compute P_other_allocations (lighting, appliances) per other NEC clauses.
- P_total = P_sabc_total + P_laundry_total + P_other_allocations.
- Compute I_feeder = P_total / V_phase (use 240 V single-phase for combined feeder conversion to amperes where applicable; confirm neutral contributions and multiwire branch circuits per NEC).
- Apply demand factors for feeders if permitted elsewhere in Article 220.
- Select conductor size with ampacity > I_feeder and comply with overcurrent protection device limits (NEC 240).
Worked example 1 — Single-family dwelling, baseline NEC allocations
Scenario:- One single-family dwelling unit.
- Minimum required small-appliance branch circuits = 2.
- Laundry allocation applicable = yes (one laundry circuit).
- Service is single-phase 120/240 V.
1) Small-appliance allocation: N_sabc = 2 × 1,500 VA = 3,000 VA.
2) Laundry allocation: P_laundry = 1,500 VA.
3) Total NEC allocated VA for small-appliance + laundry: P_total = 3,000 + 1,500 = 4,500 VA.
4) If calculating a feeder current for diversified load, convert VA to amperes. Using 240 V single-phase for feeder basis (NEC feeder calculations combine 120 V loads to arrive at net feeder ampacity; many engineers divide VA by 240 V for single-phase feeder approximation when neutral currents cancel; follow local practice):
I_feeder = P_total / 240 V = 4,500 / 240 = 18.75 A.
Interpretation and final sizing:- On a per-branch-circuit basis, each small-appliance circuit carries allocated 1,500 VA / 120 V = 12.5 A, yet each must be a minimum 20 A branch circuit per NEC 210 requirements.
- The laundry allocated current at 120 V is 12.5 A and requires a dedicated 20 A laundry circuit per NEC.
- The feeder equivalent derived above (18.75 A) indicates the feeder must be sized to support the total allocation plus other loads (lighting, heating, water heater, HVAC). Conductor/overcurrent selection for the service/feeder is performed using total load per Article 220.
- Therefore, the dwelling will have at minimum two 20 A small-appliance breakers and one 20 A laundry breaker for branch-circuit protection; service/feeder calculation will include these allocations as part of the total VA to determine main service rating (commonly 100 A or 150 A depending on additional loads).
Worked example 2 — Multifamily building, ten units, feeder sizing excerpt
Scenario:- Multifamily building with 10 identical dwelling units.
- Each unit: minimum two small-appliance branch circuits and one laundry allocation.
- Engineer must compute the small-appliance and laundry component of the common feeder.
1) Per unit small-appliance allocation = 2 × 1,500 VA = 3,000 VA.
2) Per unit laundry allocation = 1,500 VA.
3) Per unit combined allocation = 4,500 VA.
4) Building total allocation for these items: P_total = 10 × 4,500 VA = 45,000 VA.
5) Convert to feeder current using single-phase 240 V basis for feeder calculation:
I_feeder_raw = 45,000 / 240 = 187.5 A.
Apply NEC demand factors and considerations:- Article 220 includes additional rules for dwelling units, such as applying general lighting load rates and demand factors for multiple units; however, small-appliance branch circuit allocations are typically not subject to further demand multipliers across multiple units because they are per-unit allocations intended to cover receptacle loads. Confirm with the applicable NEC edition and local amendments.
- Assume no further demand reductions for small-appliance/laundry allocations for conservative design. Then the feeder must accommodate 187.5 A for these allocations alone plus other common loads (lighting, HVAC, cooking appliances) that will increase the required feeder size.
- Because 187.5 A exceeds standard single-phase main breaker sizes below 200 A, select a feeder and main service rating appropriately — commonly 200 A or greater depending on additional loads.
- For example, choose a 200 A service with properly sized conductors (e.g., 2/0 AWG copper or 4/0 AWG aluminum per NEC tables and temperature/termination considerations) subject to final ampacity calculation per NEC 310 and adjustments.
Exact conductor selection requires consulting NEC 310.16 ampacity table, considering conductor insulation, terminal temperature ratings, number of current-carrying conductors in raceway, ambient temperature adjustments, and whether the feeders serve electric ranges or other high-load appliances requiring separate calculations.
Installation and verification considerations
Practical verification steps when applying the calculations:- Confirm the adopted NEC edition at the project jurisdiction and reference the exact text for 220.52 and related articles.
- Use the NEC prescribed VA allocations for small-appliance and laundry loads — do not substitute measured loads without justification and code allowance.
- Remember that branch-circuit minimum overcurrent ratings and conductor sizes are determined by function and NEC rules — e.g., small-appliance and laundry circuits must be 20 A minimum (use 12 AWG copper conductors).
- When summing loads for feeders/services, include cooking, heating, HVAC, water heating, and other loads per Article 220 to determine final service sizing.
- Apply ampacity correction factors and conductor bundling adjustments before finalizing conductor sizes and breaker selections.
- Document calculations and retain references to the NEC sections used for permitting and inspection.
Common pitfalls and best practices
- Misinterpreting VA allocation: Remember the NEC prescribes VA values for load calculation, and these allocations are not necessarily equal to actual measured load but must be used for sizing.
- Applying demand factors incorrectly: Some allocations are fixed and others may accept demand factors; consult Article 220 subsections carefully.
- Conductor ampacity oversights: Always apply conductor correction factors (ambient temperature, conductor grouping) and terminal limits per NEC 110.14.
- Branch-circuit minimums: Despite calculated currents below 20 A, small-appliance and laundry branch circuits must be installed as 20 A circuits per NEC 210.
- Documentation: Provide full, traceable calculations for inspectors and future engineers to validate sizing decisions.
References and further reading
Normative references:- NFPA 70, National Electrical Code (NEC) — especially Article 220 (Branch-Circuit, Feeder, and Service Calculations), Article 210 (Branch Circuits), Article 310 (Conductors for General Wiring), and Article 240 (Overcurrent Protection).
- Institute of Electrical and Electronics Engineers (IEEE) standards for conductor selection and installation guidance: https://www.ieee.org
- International Association of Electrical Inspectors (IAEI) technical guidance: https://www.iaei.org
- NFPA NEC information: https://www.nfpa.org/NEC
- IAEI resources and code change commentary: https://www.iaei.org
- Mike Holt Enterprises (educational content on NEC application): https://www.mikeholt.com
Appendix: Quick-reference checklist for NEC 220.52 calculations
- Confirm jurisdictional NEC edition.
- Use 1,500 VA per small-appliance branch circuit.
- Include 1,500 VA laundry allocation per dwelling unit where applicable.
- Convert VA to amperes using I = P / V; use appropriate system voltage for feeder or branch-circuit basis.
- Design branch circuits as minimum 20 A for small-appliance and laundry circuits with 12 AWG copper conductors (or larger as required by derating).
- Document and apply conductor ampacity adjustments per NEC 310 and 110.
- Sum and include all other applicable loads for final service/feeder sizing per Article 220.