Formula Used
Lighting VA = Floor area × Lighting VA per square foot.
Small appliance VA = Number of circuits × 1500 VA.
Laundry VA = Number of circuits × 1500 VA.
Noncoincident HVAC VA = Greater value of heating VA or cooling VA.
Demandable VA = Lighting + receptacles + appliance loads + range + dryer + water heater + HVAC.
Demand adjusted VA = Demandable VA × Demand factor.
Total design VA = Demand adjusted VA + 125% continuous VA + 125% motor VA + safety margin + spare capacity.
Single phase amps = Total design VA ÷ Voltage ÷ Power factor.
Three phase amps = Total design VA ÷ √3 ÷ Voltage ÷ Power factor.
How to Use This Calculator
Enter the building area first. Then add lighting density, receptacle load, and appliance circuits.
Add fixed equipment from schedules or nameplates. Enter heating and cooling separately. The calculator uses the larger HVAC value.
Enter continuous and motor loads where needed. Set the demand factor, voltage, phase, and power factor.
Press the calculate button. Review the load, amperage, breaker guide, and density values above the form.
Use the CSV and PDF buttons to save the result for construction review.
Electrical Load Planning
Electrical load calculation protects a project before wires are pulled. It converts rooms, equipment, motors, and reserves into one service demand. A builder can compare that demand with panel size, feeder size, and future expansion needs. The method also supports early budgeting.
Why Demand Matters
Connected load is not always the same as demand load. Every device may not run at the same time. Demand factors reduce reasonable groups, while continuous loads and motors need extra allowance. This calculator keeps those parts separate. That makes the final amperage easier to review.
Construction Inputs
Start with floor area and lighting density. Add receptacle loads, appliance circuits, laundry circuits, and fixed equipment. Enter the larger heating or cooling load when they are noncoincident. Add motors, continuous equipment, reserve capacity, and a safety margin. Use actual nameplate values whenever possible. Estimates should be replaced as drawings mature.
Reviewing the Output
The result shows connected volt amperes, demand adjusted load, design load, current, and a suggested breaker level. It also reports load density. High density can reveal unusual kitchens, workshops, data spaces, or mechanical rooms. Low density may show missing equipment. Treat the answer as a design check, not a permit approval.
Field Use
During construction, the calculation helps coordinate panels, feeders, and utility service. It can also help choose temporary power. A clear record reduces changes later. Export the CSV for schedules. Export the PDF for review notes. Always compare the final design with local code, engineer comments, and utility requirements.
Good Documentation
Keep every assumption visible. Record voltage, phase, power factor, and demand percentage. Note whether heating and cooling are simultaneous. Keep spare capacity separate from safety margin. This makes review faster for owners, estimators, and inspectors.
Limits
This tool uses general formulas. It does not replace engineered design. Special occupancies may need different rules. Examples include hospitals, factories, elevators, commercial kitchens, and hazardous locations. Long feeders may also need voltage drop checks. Short circuit duties may need utility fault data. Use the calculator early, then verify every final conductor, panel, and overcurrent device.
Best Practice
Review loads after each drawing issue. Update the file when equipment changes. Small revisions can affect feeders, panels, generators, and service coordination early.
FAQs
What is an electrical load calculation?
It is a method for estimating the power demand of a building. It adds lighting, receptacles, appliances, motors, and equipment. Then it adjusts the total with demand, safety, and spare factors.
What does VA mean?
VA means volt amperes. It represents apparent electrical power. It is commonly used for service sizing because voltage, current, and power factor all affect real system demand.
Why use a demand factor?
A demand factor reflects that many loads do not operate together. It reduces suitable groups to a realistic design demand. Final values should still follow local rules and engineer review.
Why are continuous loads multiplied by 125%?
Continuous loads can run for long periods. Extra allowance helps avoid overheating and nuisance trips. This calculator applies 125% to continuous load input for conservative planning.
Why does the calculator use the larger HVAC load?
Heating and cooling often do not run at the same time. In that case, the larger load controls. Use separate rules if both loads can operate together.
Is the suggested breaker final?
No. It is a planning guide based on calculated current. Final breaker selection depends on conductors, equipment ratings, local code, fault current, and design documents.
Can I use this for commercial buildings?
Yes, for early estimates. Commercial projects may need special load categories, demand rules, diversity factors, and engineered schedules. Use this result as a starting review.
What should I export?
Export CSV for spreadsheets and schedules. Export PDF for reports, design notes, or field coordination. Keep both files with the project load documentation.