Friday, 5 July 2013

Never mind your computer, watch your router (or your set top box)

Some of my recent consulting work has been published recently [1], including a chapter on electricity used by appliances running in standby mode. The original data came from a study of 250 households during 2010/2011, with most appliances individually monitored. The results show that even when your computer and monitor have shut down into energy saving mode your modem and router carry on as normal, and are often the biggest part of your ICT electricity bill. However there are big differences between the best and worst. Here are a few facts from my research and from other articles I have found on the internet recently.

From the 250 household study

From the 250 household study, most modems use  5.4 to 8.4 W continuously, routers are similar at 3.9 to 9.3 W. The average in both cases is about 7 W so 120 kWh/year for the two together if you leave them on all the time. A desktop in energy saving mode takes on average about 3 W but could be as low as 0.3, the monitor takes even less, so you are quite likely to be spending more on electricity for your network than for computer and phones.  Finding a low power router/modem is difficult because there are no energy standards for these devices as yet. I just checked the top three combined modem/routers in Amazon and the product power consumption was specified for only one of them.

An energy star standard is under development [2] but Energy Star is a simple pass/fail which is not nearly good as the EU Energy Rating system which allows different grades.

For comparison,  a recently published National Resources Defence Council (NRDC) survey [3] in the USA tested 60 devices of various types and found that modems and routers take typically 5 W each. This is slightly less than in the UK survey which may be because the devices were newer. NRDC also found integrated gateway devices (modem/router in one) taking up to 20W - so combining the two functions does not necessarily lead to savings. NRDC reckon that across the USA these networking devices consume 1.5 GW electricity or 3 medium sized power stations and cost consumers $1 billion every year.

Back to the UK households now - many people worry about leaving the TV on standby but it only takes 1.4 W on average. The real hog, if you have one, is your set top box. Some of these take 24 W constantly - but the best take only 4 W, a factor of 6 difference. Sky recently announced an energy saving mode for some of their Sky+ boxes. In this mode they take only 0.5 W but you have to enable it explicitly.

There are no energy standards for set top boxes either at the moment, except for very simple ones that have no recording function. There is a rating system for TVs, but size a big factor too - see Energy Efficient Appliances: the ratings confusion.

Standby for chargers - an experiment

I really like this story of an experiment by Dr. David Schmidt, from University of Minnesota’s College of Food, Agricultural and Natural Resource Sciences.

Dr. Schmidt plugged a variety of chargers onto a single power strip: 4 laptops, 2 cell phones, 2 iPads, a Nook, a Nexus, and an iPod - 11 in total. He recorded the power consumption in a variety of modes:
  • Chargers only: 0 watts
  • Chargers and appliances: sleep mode and fully charged up: 8 W
  • Chargers and appliances, sleeping but charging: 150 W
  • Chargers and appliances: active and charging: 195 W
Now from my own experiments I know that older chargers often do take more power than this when the appliance is fully charged so I would definitely recommend unplugging your appliance when the battery is full, unless you have measured it  and know it is OK.  (If it is warm to the touch it is using power). The charger by itself should be fine.

[1] Early findings: Demand Side Management report (
[2] Better Home Networking Could Save $330 Million (IEEE spectrum)
[3]Small Network Equipment Energy Consumption in U.S. Homes (National Resources Defence Council)
[4] Is there Phantom Power Use in your home (Clean technica)

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