This is potentially true, but if they are running on 'smart meters' as authorized by the State of TX (and in use) customers receive real time meter monitoring in 15 minute increments. If power is intermittent, the meter updates when it's back online. So the bills that are being generated should be pretty accurate, give or take 15/30 minutes.

It's not like the old days where a meter reader would check every month. Now many customers starting in 2005 had their meters replaced with smart meters.

This is a very unfortunate (and legal) problem. Reminiscent of Enron in CA, with PG&E when the power on the grid became exponentially expensive. Although that was a man made crisis, while this is a natural disaster.