So I put the amp meter on my R3 8-zone controller. Here are my non-scientific results:
With the LED light off, the controller idles around .05A (6 watts)
With the LED light on ‘normal’, the controller idles around .056A (6.72 watts)
When I activate a zone, the controller pulls around .15A (18 watts)
Using the electricity bill calculator below, I entered in 6 watts power consumption, 24 hrs/day, and left the default kWh cost. It says the cost is about $6.50/yr.
Edit: If you are only using the controller for the summer months, for me it’s usually June through August or so, you could just unplug power to it for the 9 or so months it’s not being used. If you do this, my calculations tell me the controller will cost about $1.63/year in power consumption.