Home Electrical Load Calculator
Create a transparent preliminary load subtotal before a qualified professional applies the complete dwelling, feeder, service, equipment, and local-code calculation.
Compare up to three scenarios
Capture the current result, change one or more inputs, and see the options side by side. The first option becomes your baseline.
Your live calculator remains unchanged. Capture it only when you want a comparison point.
Save this estimate as a project section
Name rooms, roof planes, yard areas or other sections separately. CalcurHome will combine compatible results from this calculator on this device.
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View all saved project estimatesWhat does the electrical load calculator calculate?
Enter continuous watts, noncontinuous watts, an applicable demand percentage, system voltage, and an optional planning reserve. The calculator applies 125% to the continuous subtotal, adds the noncontinuous subtotal, then applies the entered factors and converts single-phase watts to amperes. It is not a dwelling service, feeder, panel, breaker, or permit calculation.
Continuous and noncontinuous single-phase load subtotal
The calculator makes each arithmetic step visible: a 125% factor is applied to the subtotal the user has classified as continuous, other watts are added, and user-entered demand and reserve percentages follow. Complete code load calculations contain classifications and methods this simplified subtotal cannot determine.
How to measure for an accurate estimate
- Build a nameplate schedule listing every fixed appliance, HVAC unit, motor, receptacle allowance, lighting load, charger, and other proposed load.
- Separate loads only after a qualified reviewer confirms which are continuous, noncontinuous, intermittent, noncoincident, or eligible for a demand method.
- Use actual equipment voltage and input ratings; do not substitute output capacity, horsepower, cooling tons, or marketing labels for electrical input.
- Document existing and proposed loads separately so additions can be compared with the approved service, feeder, panel, and utility conditions.
A transparent preliminary single-phase subtotal
A planning worksheet contains 3,000 watts correctly classified as continuous and 4,500 noncontinuous watts. It uses a 100% demand factor, 240 volts, and a 20% comparison reserve.
The continuous subtotal becomes 3,750 watts, the connected design subtotal is 8,250 watts, and the reserve raises the comparison subtotal to 9,900 watts, or about 41.3 amperes at 240 volts.Before you purchase material
- Have a qualified electrician perform the complete adopted-code load calculation before choosing service, feeder, panel, conductor, breaker, transfer, or EV equipment.
- Do not use an arbitrary demand percentage simply to reduce the result; keep 100% unless a permitted method supports another value.
- Coordinate large loads with utility service limits, equipment specifications, available fault current, and any energy-management system requirements.
- Keep the equipment schedule, calculation method, adopted code edition, local amendments, utility correspondence, and approved documents together.
Common questions
Can this calculator size my home's electrical service?
No. Residential service and feeder calculations apply detailed rules to floor area, appliance circuits, cooking, laundry, HVAC, motors, EV charging, demand factors, and other conditions. This tool only organizes two user-classified watt subtotals for professional review.
What counts as a continuous electrical load?
That is a code classification based on how the maximum current is expected to continue, not simply whether equipment is plugged in often. A qualified electrician should classify each load under the adopted code before you place its watts in the continuous field.
Why is there a demand-factor input?
Some approved load-calculation methods permit specific demand treatment for defined load groups. The field keeps that assumption visible, but it does not determine eligibility. Use 100% unless the adopted method and a qualified reviewer support a different value.
Is the planning reserve required by electrical code?
The reserve field is an optional scenario comparison, not a universal code factor. Future-load planning, spaces, capacity, energy management, and expansion requirements must be resolved from the project scope, equipment, utility rules, adopted code, and professional design.
Sources and reference standards
- NFPA 70 — National Electrical Code developmentOfficial NFPA information for the model electrical code used by adopting jurisdictions; the locally adopted edition and amendments control an installation.
- Southwire — Building Wire SelectorManufacturer reference emphasizing that final cable selection must account for installation conditions, current codes, a licensed electrician, and the authority having jurisdiction.
- OSHA — Wiring methods, components, and equipmentFederal construction-safety requirements for wiring methods, raceways, enclosures, grounding continuity, flexible cords, and temporary installations.
See every citation and the calculators that use it in the calculator source index.
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