How to calculate inverter battery backup for 150ah or 200ah 12 volt battery?

To calculate battery backup we need to consider following factors:

1. The capacity of the battery
2. The power consumption of the load
3. The voltage of the battery

Suppose, we have a 200ah battery and our total power consumption is 540 watt in approx. This consumption can be calculated considering all household electronics. For example, fan generally consume 90 watt, CFL bulbs are of 9 watt/12 watt etc.

To calculate the runtime of the battery backup, you can use the following formula:

Runtime (in hours) = Battery capacity (in Ah) x Battery voltage (in volts) / Power consumption of load (in watts)

So, for our use case

Runtime (in hours) = 200Ah x 12V / 540W = 4.44 hours (approximately)

Please comment if this is helpful.

Thanks for reading.