At 14 volts, the charging system puts out 25 amps at idle up to 46.5 amps at 3,000 RPM, so that works out to a range of approx. 350 to 650 watts.
That said, the main fuse is 40 amps (560 watts at 14 volts) and if we assume it was over-sized by 25% because it's in a hot environment, that gives a...