Saturday, March 1, 2008

My Experience with a Smart Power Strip

[Amended March 2nd. It seems the sensitivity problem with the printer, mentioned towards the end of this post, is still an issue. I will investigate further and report back, probably next Saturday.]

I recently tried out a SmartStrip surge protector from Colman Cable Inc. It is a combined power strip and surge protector intended to save electricity by automatically switching off peripheral equipment when one controlling device is switched off. It seems rugged and well made. The model I bought cost $43.95 from (there is a smaller model for $30.95) and has a total of 10 outlets: one for the control device, 6 for controlled devices, and 3 which are always live (unless you switch the power strip off). It has a lighted switch, a light to indicate whether the controlled devices are on and another to indicate that surge protection is working properly. Finally, there is a screw to control its sensitivity.

So, how useful was this in practice? Firstly one has to find a suitable application, and I had two in mind. One was entertainment. In one room I have a TV, satellite receiver, CD player, DVD player, and a tuner/amp used for the sound for everything except the DVD (because I ran out of amplifier inputs and rarely use DVD). All these devices are on standby. I also added a cordless phone charger to the mix, thinking that I listen to the radio enough to keep the phone charged and in any case there is another phone in the house. One hears a lot about not leaving things on standby and not leaving chargers plugged in when not in use, but I was not sure how much electricity was involved. Using the Cent-a-Meter described last Saturday I was unable to measure any difference very reliably – of course there could be other things going on in the house, and I might try again later with a monitor specific to the outlet – but it would seem that all these 6 devices used about 0.1 kW between them. This might not sound much, but at 16 cents per kWh it adds up to about $120 per year if left on when not needed 20 hours a day, which would pay for the SmartStrip in a few months.

I chose the tuner/amp as the control device, for two reasons: firstly, it mostly needs to be on when anything else is in use; and secondly, if it has been switched off (not on standby) it powers up with tuner on. I also found that I could not switch the satellite receiver completely off because when power returns it goes through lengthy signal acquisition process. So, this needs to be plugged into one of the permanently on outlets and the overall saving may therefore be less than 0.1 kW. Incidentally, I found that two of the devices – the tuner/amp and the satellite seem to use more power on standby than when on. I consistently measured a 0.03 kW difference on each. The TV is the only one which had a significant increase in power usage – about .15 kW – when on rather than on standby.

Now for the other case. In another room, I have a computer, external hard drive, printer, DSL internet connection, and wireless network controller. Between them they use about 0.3 kW when on. (Note that this is a case of equipment which in the past we have tended to leave on rather than just on standby. I have a computer in another room, which gets access to the internet though the network.) The internet and wireless network use transformers, and it seems these are not suitable for the controller. Likewise the computer, partly because it may not be needed when the network is and partly because it is a laptop with a charger so power consumption does not correlate well with whether it is on. So, I chose the printer as the controller. I found it quite hard to adjust the sensitivity to cope with the quite small power usage of the printer, but it now seems to be working and based upon the same assumption as above I project savings of about $350 per year.

I started out thinking the benefits would be minor, but overall savings of $470 per year on a total bill of $3000 is not to be sneezed at. Second only to the pool pump controller discussed in an earlier blog, which I estimate to be saving about $900 per year.

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