Enter Commercial Load Data
Formula Used
The calculator first finds connected load for each category. It then applies user demand factors and planning allowances.
Lighting VA = Building area × Lighting VA per square foot.
Receptacle VA = Number of receptacles × VA per receptacle.
Motor VA = Horsepower × 746 ÷ Motor efficiency ÷ Motor power factor. The demand result also adds 25% of the largest motor VA.
Demand VA = Category connected VA × Demand factor.
Adjusted demand VA = Total demand VA + Future allowance.
Service sizing VA = Adjusted demand VA + Safety margin.
Single phase amps = Service VA ÷ Voltage ÷ Power factor.
Three phase amps = Service VA ÷ 1.732 ÷ Voltage ÷ Power factor.
How to Use This Calculator
- Enter the commercial floor area and lighting load density.
- Add receptacles, dedicated equipment, kitchen loads, signs, EV chargers, and safety loads.
- Enter heating and cooling loads. Select whether they run together or not.
- Add motor horsepower values, motor efficiency, and motor power factor.
- Set demand factors for each category based on project assumptions.
- Choose voltage, phase, future allowance, and safety margin.
- Press the calculate button. Review the result above the form.
- Use the download buttons to save the estimate for design records.
Example Data Table
| Input | Example Value | Purpose |
|---|---|---|
| Building area | 10,000 sq ft | Builds the lighting load. |
| Lighting density | 1.20 VA per sq ft | Estimates general lighting demand. |
| Receptacles | 120 at 180 VA | Calculates plug load. |
| Cooling load | 45 kW | Compares HVAC load cases. |
| Largest motor | 15 hp | Adds the largest motor allowance. |
| Future allowance | 20% | Supports future tenant growth. |
| Service voltage | 208 V, three phase | Converts kVA into amps. |
Commercial Load Planning Guide
Commercial Load Planning Guide
A commercial load form supports early service sizing. It brings many small loads into one clear study. Lighting, receptacles, HVAC, motors, appliances, elevators, and safety systems can all affect the final amp rating. Good input values reduce guesswork. They also help owners compare tenant options before drawings are issued.
Why Demand Matters
Connected load is the total installed load. It assumes every device runs at once. Real buildings rarely behave that way. Demand load applies use factors to the connected load. This gives a more practical service estimate. The method is useful for offices, shops, clinics, schools, warehouses, and mixed spaces. Local codes still control the final design. The calculator gives a planning number, not a stamped design.
Key Inputs To Review
Start with floor area and lighting density. Then add receptacle counts and equipment ratings. Use nameplate values for dedicated machines. Enter the larger HVAC case when cooling and heating cannot run together. Add motors with care. A large motor may need an extra allowance because starting and running duty can stress the service. Continuous loads should be increased when they run for long periods.
Service Size Strategy
A commercial panel should not be sized only for today. Spare capacity helps with future tenants, signs, chargers, kitchen upgrades, and added mechanical units. A small planning margin can prevent expensive service changes later. Power factor also matters. Lower power factor increases current for the same useful power. Three phase systems often carry larger loads more efficiently than single phase systems.
Using Results Wisely
Review the connected load first. Then compare the demand load. Check the adjusted load after future allowance. Finally, study the recommended service current. If the result sits near a standard service size, consider the next size. Confirm utility rules, conductor sizing, voltage drop, short circuit duties, and protection settings. Keep all assumptions with the project file. Clear records make later reviews easier.
Common Review Checks
Check units before trusting any total. Kilowatts, volt amps, horsepower, and percentages mean different things. Match the form to the same voltage basis. Use conservative values when records are missing. For leased spaces, separate base building loads from tenant loads. This avoids double counting and keeps budgets clearer. These checks support safer bids and smoother plan reviews later.
FAQs
What is a commercial load calculation?
It estimates the electrical demand for a commercial space. It combines lighting, receptacles, motors, HVAC, equipment, signs, and spare capacity. The result helps plan service size, panels, and utility coordination.
Is connected load the same as demand load?
No. Connected load is the total installed load. Demand load applies demand factors because all loads may not run together. Demand load is usually the better planning value for service sizing.
Why does the form add 25% of the largest motor?
Large motors can place extra stress on a service. The added allowance gives a conservative planning adjustment. It helps account for motor duty and common electrical design practice.
Should heating and cooling be added together?
Only when they can operate at the same time. Many systems are noncoincident. In that case, the larger of heating or cooling is commonly used for planning demand.
What demand factor should I use?
Use values based on local code, project type, operating schedule, and design judgment. Keep assumptions clear. A conservative factor is better when equipment schedules are uncertain.
Why is power factor included?
Power factor affects current. A lower power factor means more current is needed for the same useful power. This can change service amperage and conductor planning.
Can this form size conductors?
No. It estimates service load and current. Conductor sizing needs code tables, temperature ratings, terminal ratings, voltage drop checks, protection settings, and installation conditions.
Why add future capacity?
Commercial spaces often change. Future capacity helps with added tenants, EV charging, signage, kitchen equipment, and mechanical upgrades. It may reduce costly service changes later.
Can I use this for a tenant improvement?
Yes, for planning. Enter the tenant loads separately when possible. Also check the base building loads to avoid double counting shared systems and existing service demand.
Does the result replace an engineer?
No. The result is an estimating tool. Final construction documents should be checked by a qualified professional and matched with local authority and utility requirements.
Why include CSV and PDF downloads?
Downloadable results help keep assumptions with the project file. They also make reviews easier for owners, contractors, estimators, and design teams during early planning.