This worksheet will help you determine the inverter and battery bank required to operate your specific loads:
Choosing the right Inverter
When sizing your inverter, calculate the total wattage required at any one time and choose the inverter with a slightly higher power output. (Start up surge should be considered for compressive loads.)
Determining your battery bank requirements
1. Converting AC amps to Watts: AC amps x 120 Volts = Watts
2. Convert Watts to Actual DC amps: (Watts / 12) x 1.1 = actual DC amps
3. amp hours consumed between charge cycles:run-time of appliance (hours) X actual DC amps = amp hours consumed
4. Number of batteries required:(Total amp hours consumed X 2*) / amp hour rating of battery = Number of batteries required*Since deep cycle batteries should only be discharged to 50% total capacity, the total amp hours consumed between charge cycles should be multiplied by 2.
amp hours consumed between charge cycle = 126
amp hour rating of battery = 90 (Group 27)
(126X2) / 90 = 2.8
(Round up to the nearest whole number.)
Therefore, the minimum number of batteries required is three with the above values.