Johnny B Good wrote:

the cost of the 16 alkaline AA cells [...] was less than the 30 to 50
quid's worth of electricity that would likely have been consumed
during that time by your typical bell transformer alone (never mind
the additional quarter to half watt consumption of a bell push
lamp).
I prefer a lit push button, so batteries are out, and I've replaced the
incandescent bulb with a pair of LEDs.

I'm sure we all know friends who have dodgy doorbells "sorry we keep
meaning to replace the battery" that you can see why the couriers tend
to knock instead of, or as well as, ringing ...