In sci.electronics.repair, on Sat, 15 Aug 2015 08:10:02 -0700 (PDT),
wrote:

It scans, as in sequential pulses tto the switches. they don't really change states much unless a key is pressed but insid the processor thigs are chaging states. That means capacitanc is loading it down, even though there is no resistive load. Stop that process and it cools down and pulls less power.

The world is getting into "green" and using/wasting less energy. they are of the mond that if a million people save a milliwatt we have collectively saved a kilowatt. Engieers, seriously, sit there and figure out how to save that milliwatt. it is partly PR and partly the governments. I hear the almost made it illegal to sell plasma TVs in the EU because they are so damn power hungry. AND GUESS WHY.

Remember about the scanning pulses and the capacitance ? Well plasma TVs are all about scanning and capacitance. I mean that is ALL they are about and in spades. A couple hundred volts at high speed applied to highly capacitive loads. It literally pulls as much juice as a old deflection yoke and high voltage circuit would.

and another ting when it comes to a keyboard, look on the bottom and see iff maybe it has a battery compartment. Seriously, some of them, even high end ones, some have a place where you can stick like eight or ten "D" cells. Do you know what good alkaline "D" cells cost ? And even in the absece of that, most of them run off DC so they know it might be run off of batteries someday.

You're right about that. I hate filling something with batteries. I
hate using batteries at all. When I was little, the only thing that ran
on batteries was a flashlight (and the car starter) and we only had one
of each.

At least one model keyboard said it took 2 AAA, which is not bad

The second one I mentioned, in the other post, is big, and I have the
image that it must need more batteries because it sends big bursts of
radio waves instead of the tiny bursts that the tiny keyboard must use.
And the keyboard is longer too, so it probably uses more energy to get
from one end to the electronics at the other end. So it needs more
batteries. At least that's how it feels.

The webpage for that other one says "Enjoy using the keyboard for a full
year** without the hassle of changing batteries. The on/off switch also
helps you save power when the keyboard is not in use. ... ** Keyboard
battery life calculation based on an estimated two million
keystrokes/year in an office environment. User experience may vary."

If I do 4000 keystrokes a year, I'll be surprised. I wish I knew if it
was a standard battery. Here it is, 2 AA batteries. That's okay.

My father bought in the '50's a tube radio that also ran on batteries.
The tube names began with 1 and 2, and maybe one was 5 because that was
the voltage the heaters used. It used two rectangular cells, and when
I was in college I thought I'd fix it up. One of them was $3 in 1966
and the 42-volt battery was for sale but it was $42 or so. That's about
$420 dollars in today's money, so I gave up the plan

that makes it a feature, actually for the customer. It is not so much that you are going to save 0.0003 cents on your electric bill next month, it might be that $15 you save on batteries next month.