That'd however work in case of EM signatures. (Could also drown e.g.
parasitic signals from a computer in added noise.) The signature of the
additional load of the aircon as it cycles on/off will stay there; the
only way to suppress that is using a UPS, and cover part of the load from
batteries (and recharge them later). In combination with a local
solar/wind generator it could even save money, in addition to increased
privacy.
Speaking about signatures, what about INTENTIONALLY creating them in the
equipment? The "Tempest Fur Elize" program allowed playing music on a
radio receiver by varying horizontal bars on a CRT monitor or even a
laptop. Demo here:
http://www.youtube.com/watch?v=F-O1QWWmVmg
http://www.youtube.com/watch?v=rm6AELkCnJY
Run a program on a computer (or a pattern of packets through a router,
perhaps no activity vs packet flood?) that creates a signature easily
recognizable on your equipment (melody for acoustic output, pattern of
peaks on a spectrum analyzer...) and then use that to examine the behavior
of the signals in your power network. A signal of known parameters can be
even fished out from below noise floor, increasing sensitivity of
detection.
There are many options. You can write your own custom program. You can use
the Tempest Fur Elize one. Or, for using the computer memory bus to
generate signal, use MemTest86, memory tester that loops through all the
address space and does nothing but read/write patterns - likely an easy to
observe regular activity.
I do not know anything about TCP/IP information
leakage into the power grid, but the whole
"Smart Grid" business assumes being able, in
the long term anyway, to read whether your air
conditioner is running full when you are not at
home, say. This is not hard in the technical
sense, but for the person who does not want to
be surveilled in this way, it is time to look
into motor/generator isolation. The narrow
technical question of the moment might be whether
a router's power signatures (as filtered off
the AC line) are proportional to TCP/IP activity.
I know nothing of what is happening, only what
is possible.
--dan