Enter the battery capacity, inverter efficiency, and load power into the calculator to determine the usage time of an inverter. This calculator helps to estimate how long an inverter can run a particular load with a given battery capacity and efficiency.

Inverter Usage Formula

The following formula is used to calculate the usage time of an inverter:

UT = (BC * 12 * IE) / LP


  • UT is the usage time (hours)
  • BC is the battery capacity (Ah)
  • IE is the inverter efficiency (expressed as a decimal)
  • LP is the load power (W)

To calculate the usage time of an inverter, multiply the battery capacity by 12 (to convert Ah to Wh assuming a 12V battery), then multiply by the inverter efficiency, and finally divide by the load power.

What is Inverter Usage Time?

Inverter usage time refers to the duration an inverter can supply power to a load before the battery is depleted. It is a crucial factor for those relying on inverters for backup power or off-grid power systems. Understanding the usage time helps in planning energy consumption and ensuring that critical loads are supported during power outages or in remote locations.

How to Calculate Inverter Usage Time?

The following steps outline how to calculate the Inverter Usage Time.

  1. First, determine the battery capacity (BC) in ampere-hours (Ah).
  2. Next, determine the inverter efficiency (IE) as a percentage and convert it to a decimal by dividing by 100.
  3. Next, determine the load power (LP) in watts (W).
  4. Next, gather the formula from above = UT = (BC * 12 * IE) / LP.
  5. Finally, calculate the Inverter Usage Time (UT) in hours.
  6. 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.

battery capacity (BC) = 100 Ah

inverter efficiency (IE) = 85%

load power (LP) = 500 W