DoD = Depth of Discharge - typically 50%
DbC = Days before Charging - typically 1.5 days
Ieff = Inverter efficiency - typically 85%

Ah = Wh / Volts x 100/DoD x DbC x 100/Ieff

Solar Batteries Calculator
Number of batteries required
Total kWh/day needed:
kWh
System volts (12,24,48)volts:
Volts
Battery volts (2,6,12)volts:
Volts
Battery capacity (Ah):
Ah
Depth of Discharge (DoD)%:
%
Inverter efficiency (Ieff)%:
%
Days before a battery Charge (DbC):
days




Example Calculations:
Not a constant load eg fridge: draws 20amps for 1sec then 0.1amps for rest of the hr...
C' = (a[amps] * t[secs])/3600(secs in an hr) + (a'[amps] * t'[secs])/3600(secs in an hr)
C' = (20 * 1)/3600 + (0.1 * 1)/3600 = 0.1055amps average current
Watt hrs = watts * hrs = run a 250W machine for 5hrs = 250 * 5 =1250Wh or 1.25kWh
Inverter efficiency (Ieff)= eg. 85% = Watthrs/efficiency = 1250/0.85 = 1470Whs or 1.5kWhs.
Watts = V * A: Amp Hrs = Watthrs/V = 1470/12 = 122.5Ahs or C = 122.5Ah, DOD = 50%
C' = C/DOD = 122.5/0.5 = 245Ah therefore need a 245Ah battery to run a 250W machine for 5hrs.

Home: requires 8.96kWh/day-night to run all the necessary appliances.
Inverter efficiency: 8.96/0.85 = 10.54kWh
No of batteries-12v system: (10.54 * 1000 * 100/DoD% * temp coefficient); Wh/12v = 1647Ah; so No Batteries = (Ah needed)/(Ah of battery) = 1647/200 = 10 x 200Ah batteries