Enter the total wattage and safety factor into the calculator to determine the inverter size.

Inverter Size Formula

The following formula is used to calculate the inverter size for a solar power system:

Inverter Size = (Total Wattage * Safety Factor) / E


  • Inverter Size is the required size of the inverter in watts
  • Total Wattage is the sum of the wattage ratings of all the devices connected to the inverter
  • Safety Factor is a factor that accounts for variations in power consumption and ensures the inverter can handle peak loads. It is typically between 1.2 and 1.5.
  • Inverter Efficiency is the efficiency rating of the inverter, expressed as a decimal. It represents the percentage of input power that is converted to usable output power.

To calculate the inverter size, multiply the total wattage by the safety factor, and then divide the result by the inverter efficiency.

What is an Inverter Size?

Inverter size refers to the maximum amount of power that an inverter can handle and convert from DC (Direct Current) to AC (Alternating Current). It is typically measured in watts or kilowatts. The size of the inverter you need depends on the total power consumption of the devices you want to run. For instance, if you want to power a 100-watt light bulb and a 500-watt refrigerator, you would need an inverter that is rated for at least 600 watts. However, it’s often recommended to get an inverter that’s rated for about 20-25% more than you’ll need, to account for power surges when appliances start up. Therefore, in this case, an inverter of around 750 watts would be appropriate. It’s important to note that a larger inverter will consume more power, even if the devices you’re running don’t require it, so it’s best to choose a size that closely matches your needs.

How to Calculate Inverter Size?

The following steps outline how to calculate the Inverter Size.

  1. First, determine the total power consumption (Watt) of all the devices that will be connected to the inverter.
  2. Next, determine the power factor of the devices. This is usually provided in the device’s specifications.
  3. Next, calculate the total apparent power (VA) by multiplying the total power consumption by the power factor.
  4. Finally, calculate the inverter size by dividing the total apparent power by the efficiency of the inverter.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem:

Use the following variables as an example problem to test your knowledge.

Total power consumption (Watt) = 5000

Power factor = 0.9

Inverter efficiency = 0.85