Mine has a power factor display and it was cheap. It shows volts, amps and watts but what is more important it shows power used over a set time. So with something like a fridge/freezer it can show if there is a fault in the thermal insulation resulting in it using more power than it should or of course the temperature being wrong.
Because my mothers freezer showed it was running 24/7 I knew there was a fault. However it did not tell me what the fault was. I tried in vain to buy a thermometer locally to measure the temperature, I had to send away for one, which then showed the thermostat was faulty.
This is the problem with the plug in devices they show there is something wrong but you need skill to both read the results and to work out what has gone wrong.
As to finding the sky box uses 20W on stand-by yes it shows it is using a lot of power (it keeps the LMB powered up) but there is very little you can do about it. Without the 24/7 power it can't find out about program changes and adjust recording times, so since we want that nothing we can do.
We found the same with an uneconomic fridge/freezer, it was using too much power, however if you consider the life to be around 7 years it did not use enough extra power to be worth changing before it failed.
So in real terms they don't really help in saving power, there are the odd items they can help with but very few. Tried using with washing machine to see which was the cheapest cycle however on a set cycle it never used the same power twice, the washer weighs the cloths and adjusts the cycle to suit and so the power used varied.
After using one it has not changed what we do one bit, it other than mothers freezer did nothing. I have measured my new fridge/freezer and freezer as new so I can compare in some years time to see if AOK but even if their not it would not cause me to change them.
