power needed x 2 = inverter power
if you needed 250 watts
250 X 2 = 500
500 would be your inverter power
inverter power / 500 = batteries @ 100ah
500 / 500 = 1 battery @ 100am
if your inverter power was 750-1000 watts you would want 2 batteries @ 100ah
if your inverter power was 2000 watts you would want 4 100ah batteries.
solar panels = 90 watts x 100ah batteries
if you had 1 100ah battery you would want 90 watts of solar panels to be useful
keep in mind that 15 watts = approx. 1 amp. an ideal charging rate is 10 amps which is about 150 watts.
if you had 2 100ah batteries you would want 180 watts of solar panels.
Don’t get me wrong, you can have a 45 watt solar panel system but don’t let your battery go flat 11.9 volts you will be days on end to top off your 100ah battery
The ideal beginner solar system would be 500 watt inverter, 1 100ah battery and 90 watts of solar panels.