Generator Calculation <

Generator calculations involvedetermining the total power demand (in kW or kVA) of your appliances, adding a safety margin, and accounting for starting surges, especially for motors, then using the appropriate formula to find the required generator size in kW or kVA, keeping in mind factors like voltage and phase (single-phase vs. three-phase).

1. Determine Your Electrical Load

List Appliances:Make a list of all the devices you want to power with the generator.

Find Wattage:Check the nameplate or owner's manual for the wattage (power consumption) of each appliance.

Convert to Watts:If an appliance's power is listed in Amperes (A), use the formula to convert it to Watts (W):Watts = Amperes Volts.

2. Calculate Total Power (kW)

Sum Watts:Add up the wattage for all your connected loads to get the total continuous running watts.

Convert to kW:Divide the total watts by 1,000 to get the total kilowatts (kW).

3. Account for Starting Loads and Safety

Starting Loads:

Identify any appliances with motors (like refrigerators, air conditioners, or pumps).These require a higher surge of power to start than to run.

Add Safety Margin:

Add 25% to your total kW load for reserve capacity and to accommodate starting surges.

4. Choose the Right Formula

Single-Phase vs. Three-Phase:

The formula changes depending on whether you have a single-phase or three-phase generator.

Convert to kVA:

Often, generator ratings are in kVA (kilo-volt-amperes), so you'll need to convert your kW to kVA:

Single-Phase:kVA = kW / Power Factor (PF)

Three-Phase:kVA = kW / (Power Factor 0.866)orkVA = kW / 0.866if PF is already 1

Note: The Power Factor (PF) for motor loads is often around 0.8.

5. Select Your Generator

Select Based on kVA:The final kVA figure will be your minimum required generator size.

Use Online Calculators:Many websites offer free calculators to help with these calculations, which can also help you estimate sizing based on home size or specific appliances.

Example:

If you have a 5 kW load, and your power factor is 0.8, you'd calculate:kVA = 5 kW / 0.8 = 6.25 kVA.Then add a safety margin for starting and select a generator with at least that kVA rating.