Why real battery backup is lower than theory
See which visible assumptions make measured battery runtime lower than a simple volts-times-Ah calculation.
Not all nominal energy is used
A planning calculation applies a usable depth of discharge instead of assuming the full label capacity is delivered.
Conversion has losses
The inverter, cables and battery discharge process reduce the energy reaching appliances. Use a manufacturer value when one is available.
Age and discharge rate matter
Battery condition, temperature, charge level and high load can change runtime. Use the calculator as a range and test your actual system safely.