Years ago I did the same here. Initially I just taped an optical sensor (CNY70) in front of the spinning disk on the old analogue electricity meter, which rotated 375 times per kWh, and hooked it up to a resistor and an ADC in between. (Note: a YouLess didn't fit, the door of the case around the circuit breaker box was far too close - about half an inch, a little over a cm - in front of the meter. So that's why a diy'd solution. Oh, and diy is more fun
)
With the measured rotation-time in milliseconds, plus the 375 rotations per kWh and a little bit of math I managed to create a highcharts-graph of the power consumption in watts of the entire house, though not a very precise graph. If I recall correctly, back then we're talking at least 200 watts idle.
Years of power saving attempts later, and also a switch to a not-smart digital meter with blinking LED that blinks once per Wh (BPW34 photodiode as sensor) and a
300 baud slow IR-port for the kWh-counters, I managed to get the idle power consumption of the entire house to as low as 68 watts and around 100W when the fridge/freezer-combo starts running.
That 68 watts consists of:
- fiber modem, not much more than a media converter, no router-functionality;
- 3 24/7 running computers (RPi and two i3 8100 era systems) plus diy 19V UPS, idles at about 15-20W total;
- TP-Link SG3216 switch that draws max 15W;
- RIPE Atlas Probe, basically a TP-Link TL-WR902AC mini router with alternative firmware;
- Idling gas-based heating system, has a very power hungry pump that only does 2 things: Nothing, and running at such a high speed that the neighbours can hear it and it's keeping me up at night, plus the power consumption when it's on is much higher than it's 20 year older predecessor;
- Idling fridge/freezer combo;
- 3 clocks, two alarm clocks and an Adafruit Ice Tube Clock with GPS-mod;
- Printer in deep sleep;
.... I believe that's about it.
For those who love graphs
If someone happens to notice something around 01:00 and 06:30, that would be the digital tv receiver/decoder (Mut@nt HD500c) with OpenPLI firmware that turns itself off around 01:00 and automatically back on at 06:30. Initially I set this up since it has a tendency to freeze after several weeks of uptime, but it also lowers the power consumption a bit. But even if I left it running, it's so much less power hungry than the provider supplied receivers/decoders that draw around 40-50 watts just by sitting there, this one a little less than 10W.