Formula Used
The calculator uses connected load, demand load, noncoincident load, and continuous load adjustments.
- Lighting load = floor area × lighting VA per square foot.
- General connected load = lighting load + small appliance load + laundry load.
- General demand = first 3000 VA + remaining VA × selected demand rate.
- Fixed appliance demand = fixed appliance total × 75%, when four or more fixed appliances are entered.
- Range demand = 8000 VA for up to 12 kW, then 5% more for each kW above 12.
- Dryer demand = entered dryer VA or 5000 VA, whichever is greater.
- HVAC demand = greater of heating VA or cooling VA.
- Continuous adjusted load = continuous VA × 125%.
- Total VA = all demanded loads + safety margin.
- Single phase amps = total VA ÷ voltage ÷ power factor.
- Three phase amps = total VA ÷ 1.732 ÷ voltage ÷ power factor.
This tool is for planning. Final electrical sizing should be checked with the adopted code and local authority.
How to Use This Calculator
- Enter the project name and floor area.
- Adjust lighting, small appliance, and laundry values.
- Add fixed appliance, range, dryer, heating, and cooling loads.
- Place EV charging and long running loads under continuous load.
- Choose voltage, phase type, power factor, and safety margin.
- Press calculate to show results below the header.
- Use CSV or PDF buttons to save the report.
Example Data Table
| Input |
Example Value |
Purpose |
| Floor area |
2200 sq ft |
Creates the base lighting load. |
| Small appliance circuits |
2 circuits |
Adds kitchen and dining receptacle demand. |
| Fixed appliance total |
6000 VA |
Represents built in appliance load. |
| Range rating |
12 kW |
Applies separate range demand. |
| HVAC values |
10000 heating, 7200 cooling |
Selects the larger noncoincident load. |
Advanced Load Planning Guide
A load calculation starts with simple project facts. The floor area creates the lighting load. Required small appliance circuits add steady kitchen demand. Laundry circuits add another base load. These items form the general load. The calculator then applies the common first block demand method. This prevents the service estimate from treating every receptacle as fully loaded. That approach gives a practical planning number. It is still only a guide.
Appliances need special attention. Fixed appliances can run together. Many dwelling methods allow a reduced demand when four or more fixed appliances are entered. The tool gives that option automatically. Ranges and dryers also receive separate demand handling. Heating and cooling are noncoincident loads. The larger value is selected. This avoids counting both systems at full size when they cannot operate together in the same design condition.
Continuous loads are handled with care. A continuous load may run for three hours or more. The calculator multiplies those values by one hundred twenty five percent. Electric vehicle charging and other long running loads can be placed in this group. Noncontinuous loads stay at their entered value. A safety margin can then be added. This helps early estimates absorb design changes.
Why Demand Factors Matter
Demand factors make service planning more realistic. Homes have many connected loads. They rarely operate at the same time. Lighting, receptacles, appliances, motors, and comfort equipment follow different use patterns. A demand method reflects that diversity. It also keeps the result organized. Each subtotal is shown before the final amperage is calculated.
Working With Results
Review every input before using the answer. Local rules may require another method. Utility requirements may also change the service size. Use the result for budgeting, design review, and comparison. Confirm final sizing with the authority having jurisdiction. The PDF and CSV exports help keep a simple record. They are useful for proposals, notes, and internal checks. Always verify breaker, feeder, grounding, and conductor choices separately.
Good Input Practices
Use nameplate ratings when available. Convert kilowatts to volt amperes carefully. Keep optional loads separate. Do not hide major equipment inside general notes. Clear entries make the exported report easier to check. They also reduce costly revision work later.
FAQs
Is this an official Mike Holt calculator?
No. It is an educational planning calculator inspired by common load calculation workflows. Always verify final design with local code, project documents, and qualified electrical review.
Can this calculator size a residential service?
It can estimate service amperage for planning. Final service size must consider adopted code, utility rules, conductor ratings, grounding, available equipment, and inspection requirements.
Why is the larger HVAC load used?
Heating and cooling are often noncoincident. That means both systems usually do not run at full design load together. The calculator uses the larger value for planning.
Why are continuous loads multiplied by 125%?
Continuous loads can operate for long periods. The added factor helps account for sustained heating and equipment duty. Use it for EV charging and similar long running loads.
What does the safety margin do?
The safety margin adds extra capacity after demand calculations. It helps early estimates handle design changes, owner options, future loads, and uncertain nameplate values.
Can I change the demand percentage?
Yes. The form includes a field for demand after the first 3000 VA. Change it when your worksheet or local method requires another value.
Why does the dryer use at least 5000 VA?
The calculator applies a common planning minimum for dwelling dryers. If the entered dryer nameplate value is higher, the higher value is used instead.
What exports are available?
The page can download a CSV file and a simple PDF report. Both include the main input summary, demand subtotals, final amperage, and recommended service size.