Not even 1 percent because electric systems within car run from alternator whereas starter motor relies on batteries. Alternators has a constant load on engine, its like a free wheel which runs at double the RPM of engine just because of ratios of pulley. Ratios of engine side pulley to alternator pulley at times is 1:2.1 which means that if engine is running at 1000 RPM while idling then alternator will be running at 2100 RPM. Energy produced from Alternator increases with increase in RPM but manufacturers inserts the alternator in Vehicle which can take the entire load of all the accessories within car from single alternator. Like if you will turn on AC, lights, indicators, fans then alternator at idling wont need an AID of battery but on top will be charging it as well. You cannot avoid the load of Free Wheel (Alternator) from your Vehicle but its upto you if you want to utilize the energy it is producing or let it go waist.
I hope, this answers your question and yes, once your vehicle is off then batteries will take the remaining load or once you insert extra load such as extra after market systems then that may demand extra energy from battery.
smaller the alternator pully diameter then higer the RPM alternator runs. don't misunderstand AC example because once AC is on the extra motor which is compressor clutch is engaged which put extra load on engine.
