Then there is the meter socket, unless existing is rated 200A. And the
service wire has to be upgraded, which requires larger conduit. And the
underground run may or may not have to be replaced depending on the
existing size and whether owned by the customer or utility. If the
utility replaces it, they may charge the customer.


In many/most places you can call the "utility" company and they will tell
you the capacity of the service.

Because the placement of the wires in the first place was a major cost of
underground service, you may find that your already have 200 amps to the
meter box.

In my case when I wanted to replace an old fuse box with a CB panel, the
electric company said I already had 200 amp to the meter. My electrician
said that the wires to the old box from the meter had 200 amp capacity. It
was just a matter of tearing down the fuse box and putting up the CB panel.

Of course the reality is that if you have been getting my for years and
years with a 100 amp (or less) service, you aren't going to stress the
service.

If anything, "modern" appliances use less power that the equivalent from 30
or more years ago.