Data on how much power an adapter or ,"wall wart" consumes when not in use, is hard to find.  One simple way of estimating it, is to see if it gets warm.

- If you can't feel any heat it must be about 1 watt or less.

- If you can feel any warmth at all it draws about 2 to 4 watts.

- If it's obvious that it's warm it could be 6 to 8 watts.

- If it's a big adapter for a laptop or a display, it would take 10 to 15 watts, to warm it, since it has a large surface area. The heavy ones have a transformer inside.

If you have 20 in the small category, with even a low 4 watt average, it's 80 watts!

You are definitely saving more power than one cordless phone base station at say... 7 watts.

Here, in this house, we have two big culprits and they are not easy to deal with. One is the internet modem. It has ventilation slots and is still very warm. Must be 35 watts or so. The other is the digital cable box.  In the morning, it's just as hot as if it were "on" all night. Another 35 watts or so. Niether has an on off switch. Both have substantial boot up time. We are in New York City with the highest electric rates in the country. Yet we hesitate to add to our morning routine the power up and boot time of these two items.

70 watts = .070 kw x 10 hrs a day, that's .7 kw x 365 days x $ 0.22 kw/hr = $56 a year.

(But only 15 cents a day to avoid the inconvenience.)         - Image streetech.com

The power consumption of a mechanical time switch could be around 1 watt which is similar to a modern unloaded mains adaptor or standby circuit. There would be a net increase in power consumption if this type were used as a power saving measure in these cases.

On the other hand, the power consumption of an electronic time switch is, at most, only a few milliwatts. This is because, to power the timer circuit, the mains voltage is dropped by a series capacitor which consumes virtually no power. It does allow a small AC current to flow to power the low voltage circuit, but as the current flows, energy is stored in the capacitor during periods of rising voltage and then returned to the mains supply as the voltage is falling.