2.4 watts reported on the kill-o-watt meterOver the last 18ish days, I have been using the Kill-o-Watt tool to monitor the electricity consumption of the Pi running openzwave for home automation and EtherRain 8 for perfect sprinkler control.

I am using apache2 and some cron jobs, but not much else is on the Raspberry Pi. I am not using a separate powered hub for the Aeon Lab ZStick S2. I run Debian 6 headless and have nothing else plugged in other than Aeon Lab S2 and my ethernet cable.

So far it has averaged about 2.45 watts an hour, putting me at 1.13ish kilowatts since I started monitoring it 18 days go. Based off this data, I think it will cost about $4.00 a year. I think I will get some small savings from having the lights on timers but nothing close to the cost of the equipment.

TL;dr – while the footprint for the Pi is really small, this is a project you do for the lols as you will not save a substantial amount of money.

Maybe Jim can share some EtherRain 8 power consumption specs and water saving ideas.

Update On Raspberry Pi Power Usage

Raspberry Pi 512mb uses 1.9 watts at idle

I tested both a UK and Chinese made Raspberry Pi Rev B 512mb RAM with nothing plugged in (no HDMI, Ethernet, USB)  and they both hovered at about 1.9 watts with the latest Rasbian install.  Plugging in the ethernet to allow it to be useful in a headless fashion, drove it to 2.2 watts.  Logging in via SSH and doing a simple ping didn’t change anything.  Running Raspbmc was a little more taxing – an unplugged board would hover around 2.1 watts.



  1. Jim -

    Hi Thomas,
    EtherRain uses an embedded microcontroller and doesn’t have near the resources of Raspberry Pi, nor does it’s micro run as fast. So power consumption is negligible. Its 50 milliamps times 5 V or about .25 Watts (1/4 Watt) in normal operation.

    I think you stand a great chance of more than recouping your investments in home automation just with the savings you’ll obtain with optimized irrigation. Most people overlook their water bill and the amount they spend on outside water. We designed OptiRain with some essential water saving features (also available on LawnCheck) while keeping it very easy-to-use. The Pi will eventually make a nice home control system – as a scheduler; and remote clients like EtherRain will let you mount your scheduler in a protected and convenient place to keep it from harm (like nasty ground surges that sprinkler controllers are frequently subject to!).

    I’ve had customers of LawnCheck tell me that they paid for their EtherRain controllers in less than 6 months in water cost savings – and OptiRain uses the same code base and provides a similar feature set.

    In California the cost of electricity is much higher than in Texas. Putting lights on automated control is a proven cost saver – of course it does depend on your current power consumption. Any kind of browser or smartphone enabled system is going to not only more than pay for the cost of the automation, but also return in convenience.

    Keep up the interesting articles.

  2. Bob Sanders -

    Great article Jim!

    Have you ever measured what the amp draw was, including spikes? Just curious.




Leave a Reply