Electrical Load Calculator
Calculate residential electrical service size using NEC Article 220 demand factors. Determine if you need 100A, 200A, or 400A service for your home.
This calculator uses NEC demand factors to determine your electrical service requirements.
General Loads
Major Appliances
HVAC (Larger of A/C or Heat Used)
Per NEC 220.60, only the larger of A/C or heating is included in the load calculation.
Demand Load Distribution
Recommended Service
200 Amps
Load Summary (NEC Demand Factors Applied)
| Load Category | Connected | Demand |
|---|---|---|
| Lighting & General | 10,500 VA | 5,625 VA |
| Electric Range | 12,000 VA | 9,600 VA |
| Electric Dryer | 5,000 VA | 5,000 VA |
| Water Heater | 4,500 VA | 4,500 VA |
| Air Conditioning | 5,000 VA | 5,000 VA |
| TOTAL | 37,000 VA | 29,725 VA |
- This is an estimate - always have a licensed electrician verify calculations
- Local codes may have additional requirements beyond NEC minimums
- Consider future loads (EV chargers, additions) when sizing service
- 200A service is becoming standard for new construction
- Demand factors reduce calculated load - actual simultaneous use is typically lower
Related Calculators
About This Calculator
Determining the right electrical service size is essential for new construction, major remodels, or adding high-draw equipment like EV chargers and heat pumps. Our Electrical Load Calculator uses NEC Article 220 standard calculation methods to determine your home's demand load and recommend the appropriate service panel size based on actual code requirements.
By applying NEC-specified demand factors, we calculate the realistic simultaneous load rather than simply adding up all connected watts. This prevents costly oversizing while ensuring your electrical service safely handles your actual usage patterns.
2026 Electrification Reality: The shift to electric vehicles, heat pumps, and induction cooking is fundamentally changing residential electrical needs. A home that was adequately served by 100A in 2010 may now require 200A or more. EV chargers alone can add 40-60A of continuous load, and heat pump water heaters plus HVAC conversion can add another 30-50A. Planning for electrification now saves the cost of multiple panel upgrades later.
Whether you're building a new home, upgrading from 100A to 200A service, or planning for future EV charging and heat pumps, this calculator helps ensure your electrical service is properly sized for today and tomorrow.
How to Use the Electrical Load Calculator
- 1Enter your home's total heated/cooled square footage for the general lighting load calculation (NEC uses 3 VA per square foot).
- 2Specify the number of small appliance circuits (kitchen counters require minimum 2 per NEC 210.11).
- 3Add major appliances: range, dryer, water heater—use nameplate wattage ratings.
- 4Enter HVAC loads including heat pump compressor and supplemental heat strips if applicable.
- 5Add EV charger requirements based on your charging needs (7.2 kW minimum per NEC 220.57).
- 6In advanced mode, add pool equipment, spa/hot tub, workshop loads, and other large circuits.
- 7Review the demand calculation breakdown showing how NEC demand factors reduce connected load to calculated load.
- 8Compare your calculated load to service size recommendations and determine if an upgrade is needed.
NEC Article 220 Standard Calculation Method
The National Electrical Code provides a standardized method for calculating residential electrical service requirements.
Step 1: General Lighting and Receptacles (220.12)
- Calculate 3 VA per square foot of living space
- Include all habitable floors, basement, garage
- This covers general lighting and receptacle outlets
Step 2: Small Appliance and Laundry Circuits (220.52)
- Add 1,500 VA per small appliance circuit (minimum 2 required)
- Add 1,500 VA for laundry circuit
- Minimum subtotal: 4,500 VA for these required circuits
Step 3: Apply General Lighting Demand Factors (Table 220.42)
| Load Amount | Demand Factor |
|---|---|
| First 3,000 VA | 100% |
| 3,001 to 120,000 VA | 35% |
| Over 120,000 VA | 25% |
Step 4: Add Fixed Appliances (220.53)
- Add nameplate ratings for dishwasher, disposal, etc.
- If 4+ appliances: apply 75% demand factor
- If 3 or fewer: 100% of nameplate
Step 5: Electric Dryer (220.54)
- Use 5,000 VA or nameplate, whichever is larger
- For multiple units: apply demand factors per table
Step 6: Electric Range/Oven (Table 220.55)
| Range Size | Demand Load |
|---|---|
| Up to 8.75 kW | 8,000 VA |
| Over 8.75 kW | 8,000 VA + 40% of excess |
Step 7: HVAC Load (220.60)
- Use the LARGER of heating or cooling (not both)
- Exception: Heat pump with supplemental heat—add both if not interlocked
Step 8: EV Charger Load (220.57)
- 7,200 VA minimum or nameplate rating (whichever larger)
- This is a continuous load—calculate at 125%
Step 9: Calculate Service Size
- Total VA ÷ 240V = Amperes required
- Select next standard service size (100A, 150A, 200A, 320A, 400A)
2026 Service Panel Upgrade Costs
Current pricing for electrical service upgrades varies by scope and region.
Panel Upgrade Costs:
| Upgrade Type | Cost Range | Time Required |
|---|---|---|
| 100A to 150A | $1,800-3,500 | 6-10 hours |
| 100A to 200A | $2,500-5,500 | 8-12 hours |
| 150A to 200A | $2,000-4,000 | 6-10 hours |
| 200A to 320/400A | $4,000-8,000 | 12-20 hours |
| New 200A service (new construction) | $1,500-3,000 | 4-8 hours |
| Sub-panel addition (100A) | $1,200-2,500 | 4-6 hours |
Cost Breakdown Components:
| Component | Typical Cost |
|---|---|
| 200A main panel | $300-600 |
| 200A meter base | $150-300 |
| Service entrance cable (4/0 Al) | $4-8/foot |
| Grounding electrode system | $200-400 |
| Permits and inspections | $100-400 |
| Utility disconnect/reconnect | $0-200 |
| Electrician labor (8-12 hrs) | $800-1,800 |
| Materials (breakers, wire, etc.) | $300-600 |
Regional Price Variations:
| Region | Cost Multiplier |
|---|---|
| Northeast | 1.15-1.30× |
| West Coast | 1.20-1.35× |
| Southeast | 0.85-1.00× |
| Midwest | 0.90-1.05× |
| Rural areas | 1.10-1.25× |
Tax Credits Available:
- Energy Efficient Home Improvement Credit: Up to 30% (max $600) when upgrade supports heat pump or EV charger installation
- Check state/local incentives for additional rebates
Common Service Panel Sizes and Applications
Standard residential service sizes and their typical applications:
100 Amp Service:
| Aspect | Details |
|---|---|
| Typical homes | Under 1,500 sq ft, built before 1970 |
| Adequate for | Gas heat, gas dryer, gas cooking, no EV |
| Calculated capacity | ~24,000 VA / 100A continuous |
| Panel slots | 20-30 spaces typical |
| NOT adequate for | EV chargers, heat pumps, all-electric homes |
150 Amp Service:
| Aspect | Details |
|---|---|
| Typical homes | 1,500-2,500 sq ft, some electric appliances |
| Adequate for | One large electric appliance + moderate loads |
| Calculated capacity | ~36,000 VA / 120A continuous |
| Panel slots | 30-40 spaces typical |
| May work for | Level 2 charger (30A) if other loads are gas |
200 Amp Service:
| Aspect | Details |
|---|---|
| Typical homes | New construction standard, 2,000+ sq ft |
| Adequate for | Full electrification including EV + heat pump |
| Calculated capacity | ~48,000 VA / 160A continuous |
| Panel slots | 40-60 spaces typical |
| Supports | EV charger + heat pump + electric range/dryer |
320/400 Amp Service:
| Aspect | Details |
|---|---|
| Typical homes | Large homes 4,000+ sq ft, multiple EVs |
| Adequate for | All-electric luxury, workshop, pool/spa |
| Calculated capacity | 76,000-96,000 VA |
| Configuration | Often two 200A panels or 400A split bus |
| Requires | Larger service entrance, utility coordination |
80% Continuous Load Rule: For loads operating 3+ hours continuously:
- 100A panel: 80A continuous capacity
- 200A panel: 160A continuous capacity
- 400A panel: 320A continuous capacity
EV Charger Electrical Requirements
Electric vehicle charging adds significant load to residential electrical systems.
EV Charger Levels and Power Requirements:
| Level | Voltage | Amperage | Power | Miles/Hour | Circuit Needed |
|---|---|---|---|---|---|
| Level 1 | 120V | 12-15A | 1.4-1.8 kW | 3-5 | Standard outlet |
| Level 2 (basic) | 240V | 24A | 5.8 kW | 15-20 | 30A circuit |
| Level 2 (typical) | 240V | 32A | 7.7 kW | 20-28 | 40A circuit |
| Level 2 (fast) | 240V | 40A | 9.6 kW | 25-35 | 50A circuit |
| Level 2 (max) | 240V | 48A | 11.5 kW | 30-40 | 60A circuit |
| Level 2 (max+) | 240V | 80A | 19.2 kW | 50-70 | 100A circuit |
NEC 220.57 EV Load Calculation:
- Minimum: 7,200 VA or nameplate rating (whichever larger)
- Continuous load: Calculate at 125% for circuit sizing
- Example: 48A charger × 1.25 = 60A breaker required
Circuit and Wire Sizing:
| Charger Amps | Breaker Size | Wire (Copper) | Wire (Aluminum) |
|---|---|---|---|
| 24A | 30A | #10 AWG | #8 AWG |
| 32A | 40A | #8 AWG | #6 AWG |
| 40A | 50A | #6 AWG | #4 AWG |
| 48A | 60A | #6 AWG | #4 AWG |
| 80A | 100A | #3 AWG | #1 AWG |
Multiple EV Considerations:
- Two EVs can require 80-120A of charging capacity
- Load management systems can share capacity between chargers
- Some utilities offer second meter for EV at reduced rates
- NEC 625.42 provides demand factors for multiple EVs
Planning Recommendations:
- Install 60A circuit even if using smaller charger now
- Run conduit to allow future wire upgrade
- Consider smart charger with load management
- Locate near panel to minimize wire runs
Heat Pump and HVAC Load Calculations
HVAC systems represent the largest loads in most homes.
Heat Pump Load Components:
| Component | Typical Load | Notes |
|---|---|---|
| Compressor (cooling) | 2-6 kW | Varies by tonnage |
| Compressor (heating) | 2-6 kW | Same as cooling |
| Air handler/fan | 500-1,500 W | Runs with compressor |
| Supplemental heat strips | 5-20 kW | Emergency/backup |
| Defrost cycle | Compressor + strips | Brief periods |
Heat Pump Sizing by Tons:
| Size | Cooling | Heating | Aux Heat | Total Max |
|---|---|---|---|---|
| 2 ton | 2,400 W | 2,400 W | 5,000 W | 7,400 W |
| 2.5 ton | 3,000 W | 3,000 W | 7,500 W | 10,500 W |
| 3 ton | 3,600 W | 3,600 W | 10,000 W | 13,600 W |
| 4 ton | 4,800 W | 4,800 W | 15,000 W | 19,800 W |
| 5 ton | 6,000 W | 6,000 W | 20,000 W | 26,000 W |
NEC 220.60 HVAC Calculation Rules:
- Use larger of heating OR cooling (not both)
- Exception: If heat pump and strips can run simultaneously, add both
- If interlocked (can't run together): use larger only
Electric Resistance Heat (No Heat Pump):
- First 10 kW: 100% demand
- Remainder: 65% demand
- Example: 20 kW = 10 kW + (10 kW × 0.65) = 16.5 kW demand
Heat Pump Water Heater Loads:
| Type | Power Draw | Annual kWh | Notes |
|---|---|---|---|
| Heat pump water heater | 500-2,000 W | 1,500-2,500 | Most efficient |
| Standard electric tank | 4,500 W | 4,000-5,000 | Moderate |
| Tankless electric | 18,000-36,000 W | 3,000-4,500 | Huge instantaneous load |
Important: Electric tankless water heaters often require 100-150A by themselves and may necessitate 320A+ service.
Sample Load Calculations
Real-world examples of NEC Article 220 calculations:
Example 1: Typical 2,000 SF Home (Gas Heat/Gas Dryer)
| Load Item | Connected | Demand Factor | Demand |
|---|---|---|---|
| General lighting (2,000 SF × 3 VA) | 6,000 VA | See below | — |
| Small appliance circuits (2 × 1,500) | 3,000 VA | Combined | — |
| Laundry circuit | 1,500 VA | Combined | — |
| Subtotal for lighting | 10,500 VA | — | — |
| First 3,000 VA | 3,000 VA | 100% | 3,000 VA |
| Remainder (7,500 VA) | 7,500 VA | 35% | 2,625 VA |
| Lighting demand | — | — | 5,625 VA |
| Electric range (12 kW) | 12,000 VA | Table 220.55 | 8,000 VA |
| Water heater | 4,500 VA | 100% | 4,500 VA |
| Dishwasher | 1,500 VA | 100% | 1,500 VA |
| A/C (4 ton) | 4,800 VA | 100% | 4,800 VA |
| Total Demand | — | — | 24,425 VA |
| Service Size | 24,425 ÷ 240 = | 102A | Use 150A |
Example 2: Modern All-Electric Home (2,500 SF)
| Load Item | Connected | Demand Factor | Demand |
|---|---|---|---|
| General lighting (2,500 SF × 3) | 7,500 VA | — | — |
| Small appliance + laundry | 4,500 VA | — | — |
| Subtotal | 12,000 VA | — | — |
| First 3,000 VA | 3,000 VA | 100% | 3,000 VA |
| Remainder (9,000 VA) | 9,000 VA | 35% | 3,150 VA |
| Lighting demand | — | — | 6,150 VA |
| Electric range | 12,000 VA | Table 220.55 | 8,000 VA |
| Electric dryer | 5,000 VA | 100% | 5,000 VA |
| HP water heater | 2,000 VA | 100% | 2,000 VA |
| Dishwasher + disposal | 2,000 VA | 100% | 2,000 VA |
| Heat pump (4 ton) | 4,800 VA | 100% | 4,800 VA |
| Aux heat strips | 15,000 VA | 65% | 9,750 VA |
| EV charger (48A) | 11,520 VA | 100% | 11,520 VA |
| Total Demand | — | — | 49,220 VA |
| Service Size | 49,220 ÷ 240 = | 205A | Use 200A min |
This example shows why 200A is now the minimum for new all-electric homes with EV charging.
When to Upgrade Your Electrical Service
Recognizing when your current service is inadequate prevents problems and enables future needs.
Clear Signs You Need an Upgrade:
| Sign | What It Means |
|---|---|
| Main breaker trips repeatedly | Service is overloaded |
| Lights dim when appliances start | Voltage drop from undersized service |
| Panel is full, no room for circuits | Cannot add new loads |
| Adding EV charger or heat pump | Major new load requires capacity |
| Replacing gas with electric appliances | Electrification needs more power |
| Insurance/sale inspection fails | Required for transaction |
| Burning smell from panel | Immediate safety concern—call electrician |
Loads That Typically Trigger Upgrades:
| New Load | Typical Amperage | Impact on 100A Service |
|---|---|---|
| EV charger (Level 2) | 40-60A | Often requires upgrade |
| Heat pump HVAC | 30-50A | May require upgrade |
| Heat pump water heater | 15-20A | Usually manageable |
| Electric tankless WH | 100-150A | Requires major upgrade |
| Induction range | 40-50A | May trigger upgrade |
| Pool pump + heater | 20-40A | Depends on existing |
| Hot tub/spa | 30-50A | Often requires upgrade |
| Workshop (welder, etc.) | 30-60A | Often requires upgrade |
Upgrade Decision Matrix:
| Current Service | Adding | Recommendation |
|---|---|---|
| 100A | EV charger only | Calculate—may need 150/200A |
| 100A | Heat pump + EV | Almost certainly need 200A |
| 100A | Full electrification | Need 200A minimum |
| 150A | EV charger | May be adequate—calculate |
| 150A | Heat pump + EV | Likely need 200A |
| 200A | Two EVs | May need load management or 320A |
| 200A | Full electric + 2 EVs | Consider 320/400A |
Alternative to Full Upgrade: Smart electrical panels (Span, Lumin, etc.) can dynamically manage loads and potentially defer upgrades by:
- Shedding non-critical loads during peak demand
- Scheduling EV charging for off-peak times
- Providing real-time load monitoring
- Cost: $2,000-5,000 installed
Future-Proofing Your Electrical Service
Plan ahead for the electrification trend that is reshaping residential power needs.
The Electrification Timeline:
| Technology | Adoption Phase | Load Impact |
|---|---|---|
| Electric vehicles | Mainstream now | +40-60A per vehicle |
| Heat pumps (HVAC) | Rapidly growing | Replaces furnace, +30-50A |
| Heat pump water heaters | Growing | +15-20A (better than tankless) |
| Induction cooking | Growing | +40-50A (similar to resistance) |
| Battery storage | Early adopter | +30-50A for charging |
| Smart panels | Emerging | Can optimize existing capacity |
New Construction Recommendations:
| Home Size | Minimum Service | Recommended | For Full Electrification |
|---|---|---|---|
| Under 2,000 SF | 200A | 200A | 200A |
| 2,000-3,500 SF | 200A | 200A | 200-320A |
| 3,500-5,000 SF | 200A | 320A | 320-400A |
| Over 5,000 SF | 320A | 400A | 400A+ |
Future-Proofing Strategies:
Option 1: Full Upgrade Now
- Upgrade to 200A or 320A immediately
- One-time cost, maximum flexibility
- Best if panel is already full or major work planned
- Cost: $2,500-8,000
Option 2: Smart Panel + Existing Service
- Install smart electrical panel
- Dynamic load management between circuits
- Can defer upgrade in some cases
- Cost: $2,000-5,000 for panel + installation
Option 3: Phased Approach
- Upgrade to 200A now
- Install second meter for EV later (utility may offer EV rates)
- Add sub-panel for workshop/garage
- Cost: Spread over time
Preparation During Construction/Remodel:
- Install oversized conduit (even if not fully wired)
- Run circuits to garage for future EV
- Pre-wire for heat pump outdoor unit
- Install dedicated circuits for potential induction range
- Include empty conduit runs for solar/battery
Load Management and Smart Panels
Smart electrical panels offer alternatives to expensive service upgrades.
How Smart Panels Work:
- Monitor real-time power usage on every circuit
- Automatically shed non-critical loads during peak demand
- Schedule high-draw appliances for off-peak times
- Enable safe operation of more loads on existing service
- Provide detailed energy usage analytics
Popular Smart Panel Options:
| Product | Type | Cost Installed | Key Features |
|---|---|---|---|
| Span | Full panel replacement | $3,500-5,000 | Individual circuit control, app |
| Lumin | Add-on to existing | $2,000-3,500 | Load management, no rewiring |
| Schneider Square D | Full panel | $3,000-4,500 | EV ready, energy monitoring |
| Eaton | Full panel | $2,800-4,000 | Smart breakers, integration |
Load Management Scenarios:
| Situation | Without Management | With Smart Panel |
|---|---|---|
| EV charging during cooking | May trip breaker | Reduces EV rate temporarily |
| A/C + dryer + range | Overload risk | Delays dryer until A/C cycles |
| Two EVs charging | Needs 320A service | Can share 200A capacity |
| Emergency backup | Manual transfer | Automatic load shedding |
When Smart Panels Make Sense:
- Service upgrade is very expensive (underground, long run)
- Only occasionally exceed capacity
- Want detailed energy monitoring
- Planning solar/battery integration
- Utility offers time-of-use rates
When Traditional Upgrade Is Better:
- Panel is already full
- Regularly exceed 80% capacity
- Adding multiple large loads
- New construction (minimal cost difference)
- Want simplest, most reliable system
Pro Tips
- 💡Calculate your actual demand load before adding major equipment—surprises are expensive, and a load calculation costs less than an emergency panel upgrade.
- 💡For new construction, install 200A minimum service even if current calculations allow 150A—the cost difference is small and future-proofs the home.
- 💡Heat pump water heaters (2-4 kW) are much easier on service capacity than electric tankless (18-36 kW) while providing excellent efficiency.
- 💡Install oversized conduit during construction even if you don't pull wire yet—future wire upgrades are much cheaper with existing conduit.
- 💡Smart electrical panels can optimize existing capacity and potentially defer upgrades, but cost $2,000-5,000 installed.
- 💡Get utility input early—they may have requirements, fees, wait times, or incentives that affect your project timeline and cost.
- 💡For EV charging, install a 60A circuit even if using a smaller charger now—the wire cost difference is minimal and allows future charger upgrades.
- 💡The 80% rule for continuous loads is critical: a 48A EV charger needs a 60A breaker, not 50A, to operate legally and safely.
- 💡Keep copies of your load calculations—they may be required for permits, insurance, or home sale documentation.
- 💡Before upgrading to 320A+, consider whether smart load management could meet your needs at lower cost.
- 💡Panel upgrades require utility coordination and typically take 2-4 weeks from permit to completion—plan ahead for time-sensitive projects.
- 💡Energy Efficient Home Improvement Credits may cover up to 30% of panel upgrade costs when supporting heat pump or EV charger installation.
Frequently Asked Questions
Calculate your total demand load using NEC Article 220 methods. If your calculated demand exceeds 80A (80% of 100A for continuous loads), or if you plan to add significant loads like an EV charger (40-60A), heat pump (30-50A), or convert from gas to electric appliances, you likely need an upgrade. Signs of inadequate service include tripping main breakers, dimming lights when appliances start, or a panel with no room for new circuits.
