In any solar power system you will find a solar charge controller. 12v/24v solar charge controller will regulate thecurrent pulled into the solar panels and convert it into a reusable 12 volt or24 volt dc power supply. Depending on the size of your residential solar powersystem you might require a 20 amp to 60 amp charge controller. The differentsize solar charge controller will be determine by the amount of input currentthat the system will have, therefore the more solar panels you have the largersize controller you will need.