Jason,
If you look at the install manual for the 912iS, each pump is listed as 10 amps max. From my own testing I see about 6 amps for one pump. So my statement regarding the max wattage is a conservative number based on one pump at its max rated current. See the “internal consumers” list below. One pump plus the other loads adds up to about 12 amps. At 13 volts that would be 156 watts. If you are in a situation with both generators failed, and running on the battery only, use only one fuel pump!
Interesting also is that if you test this on your own aircraft you will find that two pumps do not require double the current of one pump. That is because the total power is a function of the work being done by the pump(s). With two pumps in series, the flow remains essentially constant with one pump or two running, however the head pressure is additive. But, the head pressure is regulated by engine mounted regulator so that also remains similar. So in most systems the only extra work being done when two pumps are running is from the relatively small head pressure increase you see when you add the second pump.
