It’s very efficient. The net electrical energy saved using the latent heat of water is 30 to 100+ times greater than the energy required to desalinate or wastewater recycle the same volume of water.
Unfortunately, I don’t think end-to-end encryption guarantees much when it comes to legal intercept in proprietary messaging apps. The intercept functionality could be done in the client and capture data, not just metadata.
Yes, the standard withholding methods produce poor results when pay does not arrive evenly through the whole year.
It is possible for employers to use alternative methods. IRS Pub. 15-T sec. 6 has details on common alternatives and constraints.
I have no idea to what extent employers support any of these alternative methods. I imagine it's limited to employers where much of their workforce is overwithheld using the standard methods. One example might be a school district where teachers are only paid when in session.