On 22/02/2020 11:18, John wrote:


True plus the mains transformer uses power continuously. Not just
when the bell is pressed.

Seems significant.


A small SMPS - eg phone charger - uses less than 0.5 watts no-load,
often much less (let's say 0.25W). By my reckoning that's 4.4 or 2.2
kWh per year. Current cost around 60 or 30 pence per annum.

And even cheaper of course if you can take power from a pre-existing
supply (eg alarm).

--
Robin
reply-to address is (intended to be) valid