I’ve never heard of a below ground septic system that required pumps. The only pumps for drainage are for sub level bathrooms such as in basements.

There is a significant overlap of septic installations and wells and most modern wells run on electric. But if you’re toilet’s basin is full, it doesn’t need any power to flush and drain. It just won’t fill again.

They're common used in multi stage septic systems that have a perc field above the tank level. If this pump is without power for a significant time, it will cause quite a problem. However usually your tank will have enough free capacity for some hours. You don't see pumps in single tanks very often due to solids blocking the intake.

When one of the pumps on my aerobic system died a few years back it was less than 24 hours before the drains were backed up. If your soil won't pass a perc test I guess you can just go with aerobic which allows you to build pretty much anywhere. The final stage sprays effluent on your yard.

> But if you’re toilet’s basin is full, it doesn’t need any power to flush and drain. It just won’t fill again.

typically there is enough pressure in the tank to allow a flush or two. you don't operate the well pump every time there is demand.