When you price out a 2500W inverter[+] which may only be able to fire
your pump up for one and a half 15 minute sessions, then you'll have
an "issue" with your pulse rate ;-)

[+] more so even than gas generators (which have rotational inertia to
help with startup surges), you _really_ have to oversize the inverter
for the startup surge on a motor.

OK, it sounds like an inverter is probably not a cost effective option.
I've already ruled out a gas generator as well.

So, that leaves me with some kind of water tank.

A holding tank in the attic would not work very well either, as our well
feeds multiple buildings.

Is there some way an additional pressure tank can be added at the pumphouse
that will ensure that one of the tanks is always fully pressurized? I would
think just adding a 2nd tank would still leave the possibility that both
tanks could be near their empty state when the power goes off.

Maybe some kind of valve that would switch to the full tank when pressure
drops and refill the empty one?

Anthony