Electrical Load Calculator
Calculate your residential electrical service load in amperes and volt-amperes (VA) following National Electrical Code (NEC) Article 220.82 standards. Determine whether your home’s existing panel can handle central AC, heat pumps, or an EV charger.
Calculated load & panel evaluation
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What does this calculator work out?
This calculator determines the required residential electrical service size in amperes and volt-amperes following National Electrical Code (NEC) Article 220.82. By evaluating square footage, kitchen and laundry circuits, major appliances, heating, air conditioning, and EV charging, it reveals whether a 100A, 200A, or 400A panel is required.
When adding modern high-draw electrical equipment like a Level 2 electric vehicle charger, heat pump, tankless water heater, or hot tub, homeowners and electricians must verify that the home's electrical service can handle the cumulative demand safely. Simply adding breaker amperages together produces a wildly inaccurate number because appliances do not all run simultaneously at full power.
The National Electrical Code provides Article 220.82 (the Optional Calculation method) specifically for single-family homes. This standard applies proven diversity demand factors to general household loads, acknowledging that a typical home only uses a fraction of its connected wattage at any given moment. This calculator automates that exact NEC calculation, showing your net calculated load in both volt-amperes (VA) and amperes at 240 volts. It clearly indicates whether your existing service panel has adequate headroom or if a service upgrade is legally required before installing new equipment.
What numbers do you need before you start?
You need your home's finished square footage, the count of dedicated small appliance and laundry circuits, fuel types for major appliances (electric versus gas for range, dryer, and water heater), your HVAC cooling or heating wattage, EV charger power rating, and your current service panel rating.
Start with your home's finished living area, excluding unfinished basements, open porches, and garages. The NEC assigns 3 volt-amperes (VA) per square foot to cover standard interior lighting and convenience plug receptacles. Next, verify your small appliance circuits; building code requires a minimum of two 20-amp kitchen countertop circuits and one 20-amp laundry circuit, rated at 1,500 VA each (4,500 VA total).
For major appliances, check whether they run on natural gas or 240-volt electricity. Electric ranges typically draw 12,000 VA, standard electric clothes dryers draw 5,000 VA, and electric water heaters draw 4,500 VA. For air conditioning and heat pumps, input the nameplate running wattage or ton size. If planning an electric vehicle charger, check its continuous amperage (32 amps on a 40A breaker equals 7,680 VA; 48 amps on a 60A breaker equals 11,520 VA). Finally, look at the main breaker rating on your electrical panel door (typically 100A, 150A, or 200A).
How are the results calculated?
Following NEC 220.82, general loads (lighting, small appliance circuits, appliances, and EV chargers) are summed. The first 10,000 VA is calculated at 100 percent, and the remainder at 40 percent. The largest of the heating or cooling load is added directly, and the total VA is divided by 240 volts.
The mathematical structure strictly adheres to the NEC 220.82 optional calculation standard. First, general lighting load (square feet multiplied by 3 VA) is added to kitchen and laundry circuit allowances (minimum 4,500 VA) and the nameplate ratings of all fastened-in-place appliances and EV chargers.
Because these loads never operate at simultaneous peak demand, NEC 220.82(B) applies a demand factor: the first 10,000 VA of general load is assessed at 100 percent, while all remaining wattage above 10,000 VA is reduced to 40 percent. In Part C, the heating and cooling load is calculated separately. Per code, heating and air conditioning are non-coincident loads (you don't run heating and AC at the same time), so only the larger load is included. Central AC is evaluated at 100 percent, while central electric space heat is factored at 65 percent. Adding Net General Demand to HVAC Demand yields Total Calculated VA. Dividing total VA by 240 volts yields the required service amperage.
Residential Electrical Service Sizing Reference Guide
The reference guide below outlines continuous capacity limits, typical household profiles, and feasibility for heat pumps and EV charging across standard panel sizes:
| Service Size | Max VA (@ 240V) | Typical Home Profile | EV Charging Feasibility | Heat Pump / All-Electric Feasibility |
|---|---|---|---|---|
| 100 Amps | 24,000 VA | Small/older homes (< 1,800 sq ft), gas heat & water | 16A–32A EV possible with energy management / smart splitter | Not feasible with electric heat strips; marginal with central AC |
| 125 Amps | 30,000 VA | Mid-sized homes, gas heat, standard central AC | 32A EV charger feasible | Possible with high-efficiency inverter heat pump |
| 150 Amps | 36,000 VA | 2,000–2,800 sq ft homes with central AC | 32A–48A EV charger easily supported | Moderate headroom for all-electric appliances |
| 200 Amps | 48,000 VA | Modern standard (2,000–4,000 sq ft), all-electric | 48A EV charger + future second vehicle supported | Full capacity for heat pump, induction, EV, and solar backfeed |
| 400 Amps | 96,000 VA | Large homes (4,000+ sq ft), dual HVAC, pool/spa | Multiple simultaneous Level 2 EV chargers | Complete all-electric luxury home capacity with zero throttling |