It's simple to measure..
Make sure you don't have to much activity in the house (cleaning, ironing, etc.) and try to have a steady total consumption in the "Dark Bubble". The example hereafter shows a value of 1141W as the total power of all your appliances in the house. This is a real-time power value, updated every 5 seconds.
Look at the increase (+59W) and decrease (-59W) of the total power in the house as a result of switching an appliance ON and OFF.
In order to measure the standby consumption, it's not sufficient to press the OFF button of your TV. As explained previously, it is still taking some power. So take the power cord out of the outlet as this will really shutdown the TV and plug it back in after eg. 30 seconds. Repeat a number of times and watch the power increases and decreases above the dark bubble (or subtract the two total power values from each other 1200W - 1141W = 59W). This will give you the power (or standby power) for this specific appliance, TV, Computer, PS Console, ..