Lithium Battery Buying Guide

How to calculate inverter current demands

Sizing your inverter and battery so they can work within each other's limits is one of the most important steps in selecting your equipment - in this post, we show how to calculate inverter current draw from the battery's perspective
Chris G (Manager)
October 13, 2023
3 min read

The fast method for 12V:

Watts ÷ 10 = DC amp current demand

For example, a 1,000W inverter (and supplying 1,000W to AC devices) divided by 10 = 100A of battery current required - this is a rough, rounded-up way of calculating inverter/battery current demands.

The detailed method & higher battery voltages:

Watts ÷ battery voltage ÷ 90% (or 0.9) = DC amp current demand

For example, a 1,000W inverter divided by 12.8 (a lithium battery's nominal voltage is 12.8V) divided by 0.9 (90% - inverter efficiency rating) = 87A

For 24V: 1,000W ÷ 25.6 ÷ 0.9 = 43A

For 48V: 1,000W ÷ 51.2 ÷ 0.9 = 22A

Using the above, if you're looking for a TITAN Lithium battery to power your 12V inverter, we recommend:

  • Our 80Ah & 100Ah for 1,000W inverters
  • Our 120Ah for 1,500W inverters
  • Our 150Ah & above for 2,000W inverters
  • For anything above 3,000W, we recommend at least two 150Ah in a parallel connection or a higher voltage inverter & higher voltage batteries, or batteries in series

Important to note:

  • Inverter efficiency depends on voltage and the quality of the product - 24V and 48V inverters typically are 92-95% efficient.
  • Inverters can output up to double their rating for short periods of time - a 1,000W inverter can supply 1,000W continuously but could output up to 2,000W for a short period if required.
  • Watts does not change - 1,000W AC is the same as 1,000W DC.

Need to calculate Watts instead?

Watts = Volts x Amps

Products mentioned in this post:


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