What is the charging system output on a 2000 Harley Davidson Electra Glide?

It can't be more than about 15 amps. I have had my bike for 8 years and it has always dropped down to about 10.5 - 11 volts on the voltmeter at idle which isn't right. The voltage at the battery is more like 12.2 volts at idle. When you rev it up, the voltage eventually gets up to about 14 volts. I have replaced both the battery and the regulator. I think the stock alternator is too small for the load.