In the beginning, most systems were 12 volts. The systems were smaller in the past and inverters were not reliable, so often loads were operated directly from the batteries as there were many appliances available that operated on 12 volts to cater to the RV market.Now most systems operate everything from inverter output and use standard appliances. Today’s inverters are both powerful and reliable. Only the smallest systems use 12 volts these days. As the system power level increases, so should the battery voltage. Higher voltage means lower current for the same power and enables the use of smaller cabling and breakers.