Electrical Load Calculator
Our Electrical Load Calculator gives you a quick way to estimate electrical load from the equipment and electrical values you enter. You can use it to work out total connected load, estimate demand, and convert the resulting load into amperage.
Enter the electrical loads, voltage, and other relevant values below to get started.
Electrical Load Calculator
Estimate connected electrical load, demand load, kVA and current from your equipment list, voltage and electrical system configuration.
⚙ Electrical System
Set the basic system parameters⚡ Quick Start
Load a starting example🔌 Electrical Loads
Add each significant load📐 Calculation Options
Optional demand adjustmentLoad Overview
Calculation Details
Start With the Number You Actually Have
Electrical equipment is commonly labeled in watts (W), kilowatts (kW), volt-amperes (VA), or kilovolt-amperes (kVA).
The useful first step is putting those loads on the same basis.
For example:
- 1,500 W = 1.5 kW
- 5,000 W = 5 kW
- 7.5 kVA = 7,500 VA
Once the loads are expressed consistently, they can be added to determine the connected load.
But connected load is not necessarily the same thing as the load used for service sizing.
That distinction is where electrical load calculations become useful.
Connected Load vs. Demand Load
Imagine a house with an electric range, water heater, clothes dryer, air conditioner, lighting, and several other appliances.
If you simply add every nameplate rating, you get the connected load.
That number answers:
“How much electrical equipment is connected?”
A demand calculation asks a different question:
“How much electrical demand should the system be designed to accommodate under the applicable calculation method?”
Demand factors can reduce some portions of the connected load because the code recognizes that certain loads do not necessarily operate at their maximum simultaneously. NEC-based residential calculators, for example, apply specific demand rules to general loads, appliances, heating, and cooling.
This is why two buildings with the same collection of appliances can require different calculated loads depending on the calculation method and applicable rules.
The Basic Electrical Load Formula
For a simple single-phase calculation where the load is expressed in watts:
Current (A) = Power (W) ÷ Voltage (V)
For example, a 4,800 W load operating at 240 V would require:
4,800 ÷ 240 = 20 A
So the estimated current is 20 amperes.
For apparent power expressed in volt-amperes:
Current (A) = VA ÷ V
The calculation changes for three-phase systems. For a balanced three-phase load:
Current (A) = VA ÷ (√3 × Voltage)
The important detail is that voltage alone does not tell you the required service size. The applicable load calculation, phase configuration, power characteristics, continuous loads, demand factors, and equipment requirements all matter.
What Is an Electrical Load?
Electrical load is the amount of electrical power demanded by equipment connected to an electrical system.
Common electrical loads include:
- Lighting
- Receptacles
- Electric heating
- Air conditioning
- Water heaters
- Ovens and ranges
- Clothes dryers
- Pumps
- Motors
- EV chargers
- Industrial machinery
- Computers and electronic equipment
The load can be expressed in watts, volt-amperes, or related units depending on the equipment and calculation being performed.
A 10 kW heater and a 10 kW collection of smaller appliances have the same numerical power rating, but they may not be treated identically in a formal service calculation.
Why Electrical Load Calculations Matter
A load calculation is more than an arithmetic exercise.
It helps determine whether an electrical service has sufficient capacity for the equipment it is expected to supply.
This becomes particularly important when:
Installing a new electrical service
A new building needs a service capable of supplying its expected electrical demand.
Upgrading an existing panel
Adding a large air conditioner, electric heating system, water heater, or EV charger can significantly change the electrical demand.
Adding an EV charger
An EV charger can represent a substantial additional load, particularly when several chargers are installed.
Converting from gas to electric
Replacing gas appliances with electric alternatives can change the building’s electrical requirements considerably.
Adding electric heating
Electric resistance heating can create a much larger electrical load than many conventional household appliances.
Electrical Load Calculator for a Panel Upgrade
One of the most common reasons people search for an electrical load calculator is simple:
“Can my existing electrical service handle another large appliance?”
This can arise when installing:
- An EV charger
- Heat pump
- Central air conditioner
- Electric water heater
- Electric range
- Hot tub
- Workshop equipment
- Additional heating
- Solar equipment
The answer cannot safely be determined by looking only at the rating of the new appliance.
You need to consider the existing service, existing loads, calculated demand, and the requirements applicable to the new equipment.
For existing installations, some electrical codes also provide specific methods using historical metered demand rather than simply adding every nameplate rating.
Common Electrical Load Calculation Mistakes
Adding watts without considering voltage
Watts and amps are different measurements. The relationship between them depends on voltage and, for some systems, power factor and phase configuration.
Treating every appliance as if it runs simultaneously
That can produce an unnecessarily high number when an applicable demand calculation allows diversity.
Using an incorrect voltage
A 120 V calculation and a 240 V calculation can produce very different current values for the same wattage.
Ignoring continuous loads
Some electrical codes require continuous loads to be treated differently from ordinary intermittent loads.
Mixing connected load with demand load
A connected-load total is not automatically the code-calculated demand.
Assuming every country uses the NEC
The NEC is widely used in the United States, but electrical requirements vary internationally. A calculator based on NEC rules should say so clearly.
Using the calculator as a permit calculation
An online calculator can be useful for planning and checking assumptions, but it should not replace the work required for a professional electrical design or permit submission.