WAL archive space planning?

I was "planning" to turn on WAL archiving on a postgresql 9.4.11 server
that currently is running with "wal_level=hot_standby" and streaming to
a standby. I thought there would be a relationship between the rate of
pg_xlog files and archive generation. When I turned up the
archive_command/mode I found the scale of the archive target was wrong
as I had based it on the pg_xlog file creation rate.

When I turned on the archive command for a few minutes, pg_xlog dir
contained these files for the time period:

-rw------- 1 postgres postgres 16777216 Feb 17 06:47
00000001000023AC0000007F
-rw------- 1 postgres postgres 16777216 Feb 17 06:45
00000001000023AC0000007E

The archive command wrote 126, 16MB files:

-rw------- 1 postgres postgres 16777216 Feb 17 06:47
000000010000237700000056
-rw------- 1 postgres postgres 16777216 Feb 17 06:47
000000010000237700000055
-rw------- 1 postgres postgres 16777216 Feb 17 06:47
000000010000237700000054
-rw------- 1 postgres postgres 16777216 Feb 17 06:47
000000010000237700000053
...

-rw------- 1 postgres postgres 16777216 Feb 17 06:45
0000000100002376000000DC
-rw------- 1 postgres postgres 16777216 Feb 17 06:45
0000000100002376000000DB
-rw------- 1 postgres postgres 16777216 Feb 17 06:45
0000000100002376000000DA
-rw------- 1 postgres postgres 16777216 Feb 17 06:45
0000000100002376000000D9

On servers that are not nearly as busy, I observe a one-to-one
relationship between these files/rates.

Is there a good WAL archive space planning guide?

Is the way to collect planning data for this to turn on wal_debug?

TIA!