Panel Schedule Load Calculator
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Calculate
Determines VA/ft² lighting load from NEC Table 220.12 and applicable demand factors.
Panel supply voltage. Used to convert VA to amperes (A = VA ÷ V for 1-phase; A = VA ÷ (√3 × V) for 3-phase).
Auto and service-sizing modes recommend code-minimum and headroom-friendly panel sizes. Verify mode checks an existing panel ampacity.
NEC 2023 adds the 7,200 VA minimum EVSE rule (Art. 220.57). Most load rules are similar across editions; some table numbers (e.g. receptacle demand 220.44 → 220.47) and the EVSE rule differ.
FLOOR AREA
Gross floor area (outside dimensions). Used with NEC Table 220.12 VA/ft² to compute general lighting load.
DWELLING
NEC 220.52(A): minimum 2 required. Each circuit = 1,500 VA added to lighting load before demand factor tiers.
NEC 220.52(B): adds 1,500 VA to the lighting load pool before demand factor tiers.
APPLIANCES
NEC Table 220.55 demand: ranges ≤12 kW → 8 kW demand; >12 kW → 8 kW + 5% per kW above 12.
NEC 220.54: minimum 5 kW demand applies if nameplate is lower.
Electric water heater. Treated as non-continuous unless marked continuous.
Continuous = 3+ hours at max current. If checked, the 125% factor applies to the continuous bucket per NEC 215.2(A)(1) / 230.42(A).
LIGHTING
Leave blank to auto-calculate from floor area × VA/ft² (NEC Table 220.12). Enter a value to override with actual fixture load.
HVAC
kW nameplate: VA = kW × 1000. MCA: VA = MCA × V (1-phase) or MCA × V × √3 (3-phase).
Air conditioner or heat pump cooling capacity. NEC 220.60: only the larger of cooling or heating is used (non-coincident loads).
Electric furnace or strip heat. NEC 220.60 non-coincident — only the larger of cooling/heating contributes to panel demand.
HVAC equipment running 3+ hours continuously requires the 125% factor on the larger of cooling/heating.
FIXED APPLIANCES
NEC 220.53: when count ≥ 4, a 75% demand factor applies to the combined nameplate VA.
Sum of all fixed appliance nameplate VAs (dishwasher, disposal, trash compactor, etc. — exclude range, dryer, WH already entered above).
EV CHARGER
NEC 2023 Art. 220.57: EVSE demand = max(7,200 VA, nameplate VA). Always treated as continuous load.
With a listed energy management system limiting EVSE current (NEC 220.70), the controlled setpoint may be used instead of the 7,200 VA minimum. Enter the managed load as the nameplate.
Overview
Use this calculator to size an electrical panel or service from NEC Article 220 load calculations. Enter floor area, system voltage, occupancy type, and major loads (range, dryer, water heater, HVAC, EV charger, motors, fixed appliances). The calculator returns calculated demand in amperes plus two panel recommendations: a code-minimum size that meets NEC sizing rules and a headroom-friendly size that keeps utilization at 80 percent or below.
Connected load is the sum of nameplate ratings. Demand load is the NEC-adjusted value used to size the panel. Most devices do not run at maximum simultaneously, so calculated demand is normally smaller than connected load.
The calculation engine uses a bucket-based load model: continuous and non-continuous loads are separated before the final calculation. The 125 percent continuous-load factor per NEC 215.2(A)(1) and 230.42 is applied exactly once at the continuous bucket level. Total calculated load equals non-continuous bucket plus 1.25 times continuous bucket plus the 25 percent largest-motor adder per NEC 220.50. Single application of 1.25 prevents the double-counting common in spreadsheet implementations.
Two operating modes: service-sizing (recommend panel rating from loads) and verify-existing (compare calculated demand against an existing panel rating). Four occupancy classes: single-family dwelling, multi-family dwelling, commercial (office, retail, restaurant, school, hotel, warehouse, hospital), and industrial with manual demand factors. NEC editions 2017, 2020, and 2023 are supported with edition-specific article and table mapping.
How to Use This Calculator
Select building occupancy — default is single-family dwelling. Commercial occupancies cover office, retail, restaurant, school, hotel/motel, warehouse, and hospital. Industrial enables manual demand factor entry. Other is for engineered methods and AHJ-approved factors.
Select system voltage — residential uses 120/240 V single-phase 3-wire. Small commercial uses 120/208 V three-phase wye. Larger commercial and industrial uses 277/480 V three-phase wye. Custom voltage requires explicit phase-type selection.
Open Advanced parameters — enter floor area in square feet or square meters. The calculator multiplies by NEC Table 220.12 lighting VA per square foot for the occupancy. Use General Lighting Override when actual connected lighting exceeds the table minimum.
Enter dwelling-specific loads — for dwellings, enter small-appliance circuits (NEC minimum 2), confirm laundry, enter range/dryer/water heater nameplates, and HVAC cooling and heating.
Mark continuous loads — HVAC defaults to non-continuous. Mark continuous only for 24/7 production cooling. Water heater defaults to non-continuous. Commercial lighting defaults to continuous.
Enter EV charger nameplate — as VA, amps, or kW. When entered as amps, select EV charger voltage. NEC 2023 applies max(7,200 VA, nameplate). NEC 2020/2017 uses nameplate directly.
Enter largest motor and other loads — NEC 220.50 adds 25 percent of largest motor FLA. Use the Continuous Bucket for aggregate continuous loads not entered in dedicated fields.
Press Calculate — results show panel status badge, calculated demand, both panel recommendations, and utilization. For verify-existing mode, switch Calculation Mode to Verify Existing Panel and enter existing panel rating.
The calculator produces first-order NEC Article 220 load calculations suitable for preliminary design, capacity screening, and panel selection. Final design submittals require sealed engineering drawings and AHJ approval. Not modeled: per-circuit phase balancing, short-circuit current (AIC/SCCR), arc-flash labeling, voltage drop on feeders, solar PV backfeed, energy storage systems, or generator/ATS coordination.
Formula
NEC Article 220 Bucket-Based Load Model
This calculator applies the 125% continuous-load factor exactly once at the continuous bucket level, eliminating the double-counting common in spreadsheet implementations.
Step 1: Lighting Load (NEC 220.12 + 220.42)
L_connected = Floor_Area_sqft × VA_per_sqft
Occupancy VA/sq ft (NEC Table 220.12):
| Occupancy | VA/sq ft |
|---|---|
| Dwelling | 3.0 |
| Office | 3.5 |
| Store/Retail | 3.0 |
| Restaurant | 2.0 |
| School | 3.0 |
| Hotel/Motel | 2.0 |
| Warehouse | 0.25 |
| Hospital | 2.0 |
NEC Table 220.42 demand factors:
- Dwelling, hotel, warehouse: 100% first 3,000 VA; 35% next 117,000 VA; 25% above 120,000 VA
- Hospital: 40% first 50,000 VA; 20% remainder
- Office, retail, restaurant, school: 100% (no reduction)
Step 2: Dwelling Small Appliance + Laundry (NEC 220.52)
S_load = (circuits × 1,500 VA) + (laundry × 1,500 VA)
Added to lighting connected load before applying Table 220.42 tiers.
Step 3: Range (NEC Table 220.55)
- ≤ 12 kW: demand = 8,000 VA
- 12.1–27 kW: demand = 8,000 × (1 + 0.05 × N) VA, where N = whole kW above 12
Step 4: Dryer (NEC 220.54)
Dryer_demand = MAX(5,000 VA, nameplate VA)
Step 5: Water Heater + Fixed Appliances
- Water heater: 100% nameplate
- Fixed appliances count ≥ 4: total × 0.75 (NEC 220.53)
- Fixed appliances count < 4: total × 1.00
Step 6: HVAC Non-Coincident (NEC 220.60)
HVAC_demand = MAX(cooling_VA, heating_VA)
Step 7: EVSE Load (NEC 220.57 / 625.41)
NEC 2023: EVSE_load = MAX(7,200 VA, nameplate_VA)
NEC 2020/2017: EVSE_load = nameplate_VA
EVSE is always continuous (125% at bucket level).
Step 8: Largest Motor (NEC 220.50)
Motor_adjustment = Motor_FLA_VA × 0.25
Step 9: Receptacles — commercial (NEC Table 220.47 / 220.44)
First 10,000 VA × 100%
Remainder × 50%
Step 10: Bucket Assignment and Total
calculated_load_VA = non_continuous_VA
+ (1.25 × continuous_VA)
+ motor_adjustment_VA
Step 11: Ampacity
Single-phase: calculated_A = calculated_VA / V_system
Three-phase: calculated_A = calculated_VA / (V_LL × √3)
Step 12: Panel Rating Selection
Code-minimum: smallest standard ≥ calculated_A
Headroom-friendly: smallest standard ≥ (calculated_A / 0.80)
Common listed panel ratings (A): 60, 100, 125, 150, 175, 200, 225, 250, 300, 320, 400, 500, 600, 800, 1,000, 1,200, 1,600, 2,000, 2,500, 3,000, 4,000.
What is a Panel Load Calculation
A panel load calculation determines total electrical demand on a panel or service and verifies that panel ampacity is sufficient to supply connected loads. The calculation is governed by NEC Article 220, which defines demand factors that adjust nameplate ratings to reflect non-coincident operation — most devices do not run at maximum power simultaneously.
For service-sizing, the calculation supports selection of main service equipment, service entrance conductors, and the upstream utility service. For verification (before adding an EV charger or heat pump to an existing residential panel), the calculation determines whether the existing panel has capacity or whether a service upgrade is required.
The standard load calculation method (NEC 220.40, Part III) applies category-specific demand factors. The optional method (NEC 220.82 for single dwellings and 220.84 for multi-family) is an alternative procedure available when specific eligibility conditions are met. Optional method often produces smaller demand for dwellings above 10 kVA.
For three-phase wye systems with significant non-linear loads (computers, LED drivers, VFDs), additional neutral conductor capacity beyond NEC 220.61 may be needed due to triplen harmonic currents. The screening calculation does not model harmonic content.
Why the 125% Continuous Load Factor Is Applied Only Once
The 125 percent continuous-load factor is the most commonly mishandled rule in panel load calculations. Many spreadsheet implementations apply it in multiple places, compounding the multiplication:
- Step 1: commercial lighting × 1.25
- Step 2: EV charger × 1.25
- Step 3: continuous bucket × 1.25
- Step 4: panel rating ≥ load × 1.25
A load passing through three of these steps gets multiplied by 1.25 × 1.25 × 1.25 = 1.953 — almost double its intended value. A 9,600 VA EV charger becomes 18,750 VA; a panel that should be 200 A gets pushed to 400 A.
This calculator applies 1.25 once, at the continuous bucket:
calculated_load = non_continuous_bucket
+ (1.25 × continuous_bucket)
+ 25% largest motor adder
No further multiplication occurs at panel selection. Code-minimum recommendation is the smallest standard rating meeting calculated load directly. Headroom-friendly targets 80 percent utilization through division (calculated / 0.80), not another multiplication.
Code-Minimum vs Headroom-Friendly Panel Size
The calculator produces two recommendations. Each answers a different question.
Code-minimum is the smallest standard panel rating meeting or exceeding calculated load. The calculated load already includes the 125 percent continuous factor (applied once), so code-minimum is fully NEC-compliant. Best for installations where future load additions are not anticipated.
Headroom-friendly is the smallest standard panel rating that keeps utilization at or below 80 percent. The target matches the practical loading limit for standard 80-percent-rated overcurrent equipment under continuous load and leaves 20 percent margin for future additions.
Example: calculated load 139.7 A.
- Code-minimum: smallest standard ≥ 139.7 = 150 A (utilization 93.1%)
- Headroom-friendly: ≥ 139.7 / 0.80 = 175 A (utilization 79.8%)
The status badge defaults to the headroom-friendly choice; code-minimum is shown as the NEC-compliant floor.
NEC 2023 EVSE 7,200 VA Rule (NEC 220.57)
NEC 2023 added Article 220.57 to address EV charger load calculations. The rule:
EVSE load = larger of 7,200 VA or nameplate VA
The 7,200 VA value is based on a 30 A × 240 V single-phase EVSE. The rule eliminates ambiguity that existed in earlier editions, where EVSE was treated under generic continuous-load rules from Article 625.41 without an explicit floor for small chargers.
EVSE load at 240 V single-phase by charger size:
| Charger | Nameplate VA | NEC 2023 Load |
|---|---|---|
| 16 A | 3,840 VA | 7,200 VA |
| 24 A | 5,760 VA | 7,200 VA |
| 30 A | 7,200 VA | 7,200 VA |
| 32 A | 7,680 VA | 7,680 VA |
| 40 A | 9,600 VA | 9,600 VA |
| 48 A | 11,520 VA | 11,520 VA |
After the floor or nameplate is determined, the continuous-bucket 125 percent factor applies once. A 16 A charger contributes 7,200 × 1.25 = 9,000 VA to calculated load.
For NEC 2020 and 2017 jurisdictions, Article 220.57 does not apply. EVSE load equals nameplate VA directly, with 125 percent continuous treatment at the bucket level.
Verify Existing Panel Capacity
Verify-existing mode compares calculated demand against an existing panel rating. The right tool when adding an EV charger, converting from gas to electric, evaluating older services for electrification, or verifying utilization for commercial tenant changes.
The output reports calculated demand, existing panel rating, utilization percentage, headroom to 80 percent, headroom to 100 percent, and status verdict (NORMAL, LIMITED-HEADROOM, or PANEL-UNDERSIZED).
PANEL-UNDERSIZED means calculated demand exceeds panel rating — upgrade or load reduction required. LIMITED-HEADROOM means the panel is code-compliant for present load but utilization exceeds the 80 percent planning threshold.
Enter the panel rating as the smaller of busbar rating or main breaker rating. A 200 A busbar with a 150 A main breaker has 150 A of present-load capacity — enter 150 A.
Key Facts
- The 125% continuous-load factor is applied exactly once at the continuous bucket level — not separately to each continuous load type. Multiple applications inflate demand by up to 1.25³ = 1.95×.
- NEC 2023 Article 220.57 requires EVSE load = max(7,200 VA, nameplate). A 16 A × 240 V charger (3,840 VA nameplate) counts as 7,200 VA, contributing 9,000 VA to calculated load after the 125% bucket factor.
- Code-minimum panel rating is the smallest standard rating ≥ calculated demand (NEC-compliant). Headroom-friendly is the smallest standard keeping utilization ≤ 80% (leaves room for future additions).
- NEC 220.60 allows non-coincident HVAC: only the larger of cooling vs heating enters calculated demand. For heat-pump with supplemental electric heat that can run simultaneously, enter the combined value.
- NEC 220.53 applies a 75% demand factor when four or more fastened-in-place appliances (excluding range, dryer, water heater, HVAC, motors, EVSE) are connected to the same feeder.
- A panel at 85% utilization where calculated load already includes the 125% continuous factor is code-compliant per NEC 215.2(A)(1). The 80% threshold is a planning advisory, not an absolute panel limit.
- A subpanel fed from the main panel does not reduce the load on the main panel — the subpanel contributes its load back to the main. Subpanels add breaker spaces, not ampacity.
- NEC 220.50 adds 25% of the largest motor's FLA to total load. Only the single largest motor receives this adjustment; other motors are included at FLA in the appropriate bucket.
- NEC 220.82 (single dwelling) optional method: 100% first 10 kVA + 40% remainder. Available when total connected load > 10 kVA and single feeder serves the dwelling.
- Panel busbar rating and main breaker rating may differ. A 200 A panel with a 150 A main breaker has 150 A of present-load capacity — always enter the smaller value for verify-existing mode.
- Three-phase ampacity uses the √3 factor: VA / (V_LL × √3). For 480 V three-phase, the formula divisor is 480 × 1.732 = 831.4. Using single-phase formula at three-phase voltages produces results almost 2× higher than correct.
- NEC Table 220.55 range demand: ≤ 12 kW nameplate → 8 kW demand. Above 12 kW: 8 kW + 5% per kW (or major fraction) above 12. Above 27 kW requires special calculation not covered by simple table formula.
Applications
- Residential service upgrades — older dwellings with 100 A or 150 A services often need upgrade when adding EV chargers, heat pumps, induction cooking, or electric tankless water heaters.
- New residential construction — size service for new dwellings with all planned equipment. Optional NEC 220.82 output shown alongside standard method when dwelling load exceeds 10 kVA.
- Commercial tenant fit-outs — office build-outs, retail remodels, restaurant tenant improvements with appropriate NEC Table 220.42 and Table 220.47 demand factors.
- Multi-tenant residential service — apartment building sizing using NEC 220.84 optional method with per-unit demand × Table 220.84 demand factor by unit count.
- Energy auditor capacity studies — pre-upgrade audits for EV charger installation, heat pump conversion, and electrification programs. Utilization regime quickly identifies panels with abundant headroom vs constrained vs overloaded.
- Plan check verification — AHJ plan checkers verify submitted calculations against NEC Article 220. The itemized output with NEC table references supports quick verification.
- Industrial preliminary sizing — Industrial occupancy enables manual demand factor entry where standard Article 220 default tables do not apply.
- EV charging infrastructure planning — EVEMS (NEC 750) notice fires when EV charger load constrains panel capacity, alerting to load-management option before requiring full service upgrade.
Example Calculation
Example 1 — 2,000 sq ft Single-Family Dwelling (NEC 2023)
Inputs: 120/240 V single-phase, 2,000 sq ft, 2 small appliance circuits, laundry, 12 kW range, 5 kW dryer, 4.5 kW water heater, 5 kW HVAC cooling, 8 kW HVAC heating, 3 fixed appliances (2,400 VA total). NEC 2023.
Lighting + small appliance + laundry: 6,000 + 4,500 = 10,500 VA combined. Table 220.42: 3,000 × 100% + 7,500 × 35% = 5,625 VA demand.
Range (12 kW ≤ 12 kW): 8,000 VA demand. Dryer: max(5,000, 5,000) = 5,000 VA. Water heater: 4,500 VA. Fixed appliances (3 < 4): 2,400 VA × 100% = 2,400 VA. HVAC non-coincident: max(5,000, 8,000) = 8,000 VA.
Bucket totals: non-continuous 33,525 VA, continuous 0, motor adjustment 0.
Calculated load: 33,525 / 240 = 139.7 A
Result: NORMAL / HIGH-LOAD | Code-minimum: 150 A | Headroom-friendly: 175 A (79.8% utilization)
Example 2 — Verify 200 A Panel with 40 A EV Charger (NEC 2023)
Inputs: 120/240 V, existing 200 A panel, 3,500 sq ft, 14 kW range, 5 kW dryer, 4.5 kW water heater, 10 kW HVAC heating, 5 fixed appliances (4,800 VA), 40 A × 240 V EV charger. NEC 2023.
Lighting + small appliance + laundry: 15,000 VA combined → 7,200 VA demand. Range (14 kW, 2 kW over 12): 8,000 × 1.10 = 8,800 VA. Dryer: 5,000 VA. Water heater: 4,500 VA. Fixed appliances (5 ≥ 4, 75%): 4,800 × 0.75 = 3,600 VA. HVAC: 10,000 VA. EVSE NEC 2023: max(7,200, 9,600) = 9,600 VA [continuous].
Buckets: non-continuous 39,100 VA | continuous 9,600 VA × 1.25 = 12,000 VA. Calculated load: 51,100 / 240 = 213.0 A.
Result: PANEL-UNDERSIZED | 213.0 A > 200 A | Code-minimum upgrade: 225 A | Headroom-friendly: 300 A
EVEMS-AVAILABLE-NOTICE fires: NEC 750 load management may reduce EVSE calculated load without panel upgrade.
Standards & References
- NFPA 70, National Electrical Code (NEC), 2023 edition — Primary standard for branch-circuit, feeder, and service load calculations. Article 220 governs demand factor methodology; Article 215 and 230 govern 125% continuous-load requirement; Article 408 covers panelboards; Article 625 covers EV chargers; Article 750 covers energy management systems (EVEMS).
- NEC Article 220 — Branch-Circuit, Feeder, and Service Load Calculations (UpCodes) — Readable reference for NEC Article 220 text including demand factor tables (220.42, 220.47/220.44, 220.53, 220.54, 220.55) and optional methods (220.82, 220.84).
- NEC 220.57 — Electric Vehicle Supply Equipment (EVSE) Load (UpCodes) — NEC 2023 article specifying EVSE load = max(7,200 VA, nameplate). This rule was added in NEC 2023; earlier editions use nameplate × 125% continuous treatment.
- Eaton — NEC 2023 Home Electrification and EVSE Summary — Industry explanation of NEC 2023 Article 220.57 EVSE load rule and its impact on residential service calculations.
- UL 67 — Standard for Panelboards — Common listed panelboard construction and rating reference. Specific panelboard availability varies by manufacturer and equipment series.
- IEEE Std 141-1993 (withdrawn November 2023) — Recommended Practice for Electric Power Distribution for Industrial Plants (Red Book). Industrial load calculation context. Consult the IEEE 3000-series Color Books for current industrial design guidance.
Units
The calculator supports Imperial and Metric units through the site's global unit toggle.
- Floor area — square feet (default) or square meters. 1 sq m = 10.7639 sq ft.
- Voltage — V below 1 kV. Panel system voltages: 120/240 V, 120/208 V, 277/480 V, 240 V delta, 480 V delta, or custom.
- Current — amperes (A). Values ≥ 1,000 A display with comma separator: 1,200 A, 2,500 A.
- Power — VA below 1,000 VA; kVA above 1,000 VA. kW inputs convert to VA at unity power factor (MCA input preferred for HVAC with significant PF deviation).
- Percentage — utilization and demand factors as percent. Demand factor multipliers in details as decimals (0.35 = 35%, 1.25 = 125%).
- Standard panel ratings — integer amperes: 60, 100, 125, 150, 175, 200, 225, 250, 300, 320, 400, 500, 600, 800, 1,000, 1,200, 1,600, 2,000, 2,500, 3,000, 4,000 A.
Limitations
- Circuit-by-circuit panel schedule with per-pole phase assignment and per-leg balancing — not modeled. v2.0 outputs demand load calculation for panel ampacity selection, not a circuit schedule document.
- Short-circuit current, available fault current (AIC), and SCCR per NEC 110.10 / IEEE 1584 — not modeled.
- Arc-flash labeling per NFPA 70E / IEEE 1584 — not modeled.
- Voltage drop on feeder runs — not modeled. Use the Voltage Drop Calculator for conductor sizing after panel selection.
- Harmonic THD impact on neutral sizing beyond screening notice — not modeled. Three-phase wye systems with significant non-linear loads may require additional neutral capacity.
- Commercial kitchen equipment per NEC Table 220.56 (demand factors for 3–6+ units) — not modeled. Aggregate kitchen equipment manually as fixed appliances for restaurant occupancies.
- Show window or sign lighting (NEC 220.43: 200 VA per linear foot) — not a separate input. Include in general lighting override or continuous bucket.
- Multi-range or multi-dryer demand table calculations (NEC Table 220.55 for multiple ranges, Table 220.54 for multiple dryers) — not modeled. Aggregate manually for multi-appliance projects.
- NEC 517 hospital critical-branch and life-safety-branch detail — not modeled. Hospital occupancy uses basic NEC Table 220.42 lighting demand only.
- Solar PV backfeed and NEC 705 busbar rules — not modeled. This calculator provides load-side capacity screening; PV backfeed requires separate analysis.
- Energy storage system (ESS) per NEC Article 706 — not modeled.
- Generator and automatic transfer switch sizing — not modeled.
- Automatic EVEMS load reduction — not auto-computed. Enter EVEMS-managed current as the EV charger nameplate when installed and configured.
- Heat-pump supplemental heat coincidence — not auto-computed. Enter the combined value (compressor + supplemental) in the heating field when both can run simultaneously.
Common Mistakes to Avoid
- Double-counting the 125% continuous-load factor. Applying 1.25 to commercial lighting, EV charger, continuous bucket, and again at panel selection — a load through three steps gets 1.25³ = 1.953× its value.
- Treating HVAC as continuous by default. Most thermostat-cycled HVAC does not meet the NEC Article 100 3-hour test. Mark continuous only for 24/7 production cooling, data centers, or constant-load installations.
- Citing NEC 220.50 for water heaters. NEC 220.50 governs motors. Water heaters are fixed appliances at 100% nameplate.
- Suggesting a subpanel reduces main panel load. A subpanel fed from the main contributes its load back to the main. Subpanels add breaker spaces and organization, not ampacity.
- Confusing panel busbar rating with main breaker rating. A 200 A panel can have a 150 A main breaker. Present-load capacity is the smaller of the two.
- Confusing breaker spaces with available ampacity. Empty breaker spaces do not indicate spare capacity. Adding circuits requires recalculating demand.
- Forgetting the NEC 2023 EVSE 7,200 VA minimum. A 16 A × 240 V charger (3,840 VA nameplate) counts as 7,200 VA under NEC 2023 Article 220.57.
- Entering EV charger amps with the wrong voltage. A 40 A charger on 240 V is 9,600 VA; on 208 V it is 8,320 VA. Always enter actual charger voltage from the nameplate.
- Using kW for HVAC when MCA is available. HVAC nameplates list MCA (Minimum Circuit Ampacity) per NEC 440.34, which accounts for motor inrush. MCA × voltage gives more accurate VA than mechanical kW at unity power factor.
- Assuming 100%-rated breakers without listed equipment. Most residential and small commercial breakers are 80%-rated for continuous load. Equipment listed for 100% continuous operation is uncommon.
Frequently Asked Questions
Why does my panel load calculation differ from other calculators?
What is the difference between code-minimum and headroom-friendly panel size?
When does the 80 percent threshold apply?
How does the NEC 2023 EVSE rule work for small chargers?
When should I use the optional NEC 220.82 method?
Can I add a 40 amp EV charger to a 200 amp panel?
Does a subpanel increase electrical capacity?
What is the difference between connected load and demand load?
Should HVAC be considered continuous load?
What if my panel has a 200 A bus but 150 A main breaker?
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Calculate
Determines VA/ft² lighting load from NEC Table 220.12 and applicable demand factors.
Panel supply voltage. Used to convert VA to amperes (A = VA ÷ V for 1-phase; A = VA ÷ (√3 × V) for 3-phase).
Auto and service-sizing modes recommend code-minimum and headroom-friendly panel sizes. Verify mode checks an existing panel ampacity.
NEC 2023 adds the 7,200 VA minimum EVSE rule (Art. 220.57). Most load rules are similar across editions; some table numbers (e.g. receptacle demand 220.44 → 220.47) and the EVSE rule differ.
FLOOR AREA
Gross floor area (outside dimensions). Used with NEC Table 220.12 VA/ft² to compute general lighting load.
DWELLING
NEC 220.52(A): minimum 2 required. Each circuit = 1,500 VA added to lighting load before demand factor tiers.
NEC 220.52(B): adds 1,500 VA to the lighting load pool before demand factor tiers.
APPLIANCES
NEC Table 220.55 demand: ranges ≤12 kW → 8 kW demand; >12 kW → 8 kW + 5% per kW above 12.
NEC 220.54: minimum 5 kW demand applies if nameplate is lower.
Electric water heater. Treated as non-continuous unless marked continuous.
Continuous = 3+ hours at max current. If checked, the 125% factor applies to the continuous bucket per NEC 215.2(A)(1) / 230.42(A).
LIGHTING
Leave blank to auto-calculate from floor area × VA/ft² (NEC Table 220.12). Enter a value to override with actual fixture load.
HVAC
kW nameplate: VA = kW × 1000. MCA: VA = MCA × V (1-phase) or MCA × V × √3 (3-phase).
Air conditioner or heat pump cooling capacity. NEC 220.60: only the larger of cooling or heating is used (non-coincident loads).
Electric furnace or strip heat. NEC 220.60 non-coincident — only the larger of cooling/heating contributes to panel demand.
HVAC equipment running 3+ hours continuously requires the 125% factor on the larger of cooling/heating.
FIXED APPLIANCES
NEC 220.53: when count ≥ 4, a 75% demand factor applies to the combined nameplate VA.
Sum of all fixed appliance nameplate VAs (dishwasher, disposal, trash compactor, etc. — exclude range, dryer, WH already entered above).
EV CHARGER
NEC 2023 Art. 220.57: EVSE demand = max(7,200 VA, nameplate VA). Always treated as continuous load.
With a listed energy management system limiting EVSE current (NEC 220.70), the controlled setpoint may be used instead of the 7,200 VA minimum. Enter the managed load as the nameplate.