Transformer It has always bothered me that my house’s doorbell transformer draws (according to my calibrated power electronics finger) about 2 watts of standby (no-load) power. It is always warm to the touch. Doorbell transformers are deliberately designed to be inefficient to meet the UL requirements for “inherently limited” power sources. It’s 2014 and there’s just no reason for that.

It’s not that I like to waste my time putting life’s little problems ahead of the big ones, but when I installed a second doorbell chime upstairs a few months ago, I discovered that a standard 10 VA doorbell transformer does not have enough juice to ring two doorbells at once.1 A perfect excuse for a Digi-Key order.

A modern Level V wall wart is perfectly safe, draws less than 0.3 W of standby power, and costs about the same as an iron transformer. Why are these not standard equipment for doorbells today?


  1. I also tore out two generations of unreliable wireless stick-on doorbell systems. It appears that they were installed when the hard-wired doorbell stopped working due to corroded switch contacts. More than a century of research into making reliable switch contacts has also been ignored by the doorbell industry.