Load Calculation Tool (Panel Sizing)
Calculate total electrical load for a home or building and determine minimum service panel size — with NEC 125% continuous load adjustment and PASS/FAIL compliance check for your selected panel.
Load Details
W
W
W
W
W
W
Live Results
Recommended Panel Size
125A
PASSSelected panel: 200 A
Total Load
25,500W
Total Amps
106.25A
Voltage
240V
Continuous Load
No
Load Breakdown
General Load3,000 W
HVAC Load5,000 W
Range Load8,000 W
Dryer Load5,000 W
Water Heater Load4,500 W
Additional Load0 W
Load calculations follow NEC continuous load guidelines. Always verify final design with local electrical code and a licensed electrician.
How to Use This Load Calculation Tool
- Enter general and appliance loads. Input wattage for general lighting and receptacle circuits, HVAC equipment, electric range, clothes dryer, water heater, and any additional dedicated loads. Use nameplate ratings from appliances or calculated values from a load survey — leave unused categories at 0 W.
- Select system voltage. Choose 120 V for single-phase branch-circuit planning or 240 V for whole-home service panel sizing. Total amperage is calculated as total wattage divided by voltage — 240 V service halves the ampere demand compared to the same watt load on 120 V.
- Mark continuous general load if applicable. Check Continuous Load when the general load category includes equipment expected to run for 3 hours or more — the NEC 125% multiplier applies to general load wattage only. Dedicated appliance loads (HVAC, range, dryer, water heater) are entered at full nameplate wattage.
- Select your existing or planned panel size. Choose a panel size from the standard list (100 A through 400 A) to run a PASS/FAIL compliance check against the calculated minimum. The recommended panel is the smallest standard size that meets or exceeds total amperage demand.
- Review results, warnings, and related tools. Compare total load, total amps, and recommended panel size against your selection. Review high-service and large-HVAC warnings, then verify breaker sizing, wire gauge, and voltage drop with the related electrical calculators before final design.
Formulas & Example
Panel sizing sums all load categories, applies the NEC continuous load multiplier to the general load when applicable, converts total wattage to amperage, and selects the smallest standard panel size.
Adjusted General Load = General Load × (Continuous ? 1.25 : 1.00)
Total Load (W) = Adjusted General + HVAC + Range + Dryer + Water Heater + Additional
Total Amps (A) = Total Load ÷ Voltage
Recommended Panel = smallest standard size ≥ Total Amps
Standard panel sizes (A):
100, 125, 150, 200, 225, 400Worked Example
A typical all-electric home on 240 V service with no continuous general load adjustment:
General Load = 3,000 W
HVAC Load = 5,000 W
Range Load = 8,000 W
Dryer Load = 5,000 W
Water Heater = 4,500 W
Additional Load = 0 W
Voltage = 240 V
Continuous Load = No
Total Load = 3,000 + 5,000 + 8,000 + 5,000 + 4,500 + 0 = 25,500 W
Total Amps = 25,500 ÷ 240 = 106.25 A
Standard sizes ≥ 106.25 A: 125, 150, 200 …
Recommended Panel = 125 A
Selected Panel (200 A): PASSPair this tool with the Breaker Size, Wire Gauge, Voltage Drop, and Generator Sizing calculators to complete conductor, overcurrent, and backup power planning for the same load profile.
Frequently Asked Questions
How do I size an electrical panel?▾
Add all load wattages by category, apply the NEC 125% multiplier to the general load if it is continuous, then divide total watts by service voltage to get amperage demand. Select the smallest standard panel size (100, 125, 150, 200, 225, or 400 A) that meets or exceeds that amperage. For a typical 2,400 sq ft home with electric range, dryer, and water heater on 240 V service, total demand often falls between 100 A and 200 A — but every project requires a site-specific load calculation.
What is a continuous load?▾
A continuous load is defined by the NEC as a load where the maximum current is expected to continue for 3 hours or more. In this calculator, checking Continuous Load applies the 125% multiplier to the general load category — covering lighting, receptacles, and small appliances that run extended hours. Dedicated circuits for HVAC, ranges, dryers, and water heaters are entered separately at nameplate wattage.
Does voltage affect panel sizing?▾
Yes — total amperage equals total wattage divided by voltage. The same 25,500 W load draws 212.5 A on 120 V service but only 106.25 A on 240 V service. Residential main panels are almost always sized on 240 V single-phase service because double-pole breakers deliver power at 240 V. Using the wrong voltage in the calculation will produce an incorrect panel recommendation.
What loads contribute the most?▾
Electric ranges (typically 8,000–12,000 W), central HVAC (3,000–8,000 W+), electric dryers (5,000 W), and electric water heaters (4,500 W) are usually the largest contributors in all-electric homes. General lighting and receptacle loads are often 3,000–5,000 W. Pool equipment, EV chargers, and workshop circuits can push demand above 200 A — use the Additional Load field for those dedicated circuits.
Should I oversize my panel?▾
A modest margin above calculated minimum demand is good practice for future circuits — EV chargers, heat pumps, and shop equipment are common additions. Oversizing too far increases material cost without benefit. Undersizing creates nuisance tripping and code violations. If total demand exceeds 200 A, consider 225 A or 400 A service and verify utility transformer capacity with your local power company and AHJ.
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