Green Lives Charger

Energy saving tips often include advice to avoid leaving gadgets on standby and chargers plugged in when not in use. But how do you know how much energy they use? Even if you have an OWL type energy monitor attached the power supply, these items will not register. One way is to use a plug-in power and energy monitor. This is a device that plugs into the mains and into which you plug the gadget.

When we checked our gadgets back in 2005, we found that the worst culprit was an early 1990s music system which ticked over at around 14 watts in standby mode. As we hardly used it anyway, it got switched off at the mains (a saving of around 122 kWh per year and approximately £15).

We recently ran another check on the gadgets and chargers in use in our home. Some of the results surprised us.

Chargers: In the main, our chargers registered less than 1 watt when plugged in without the gadget. So, it seems that modern chargers - usually smaller and not warm to the touch - are better than their predecessors. (Chargers tested: Kindle, iPod, Nokia phone, electric toothbrush, Philips hand mixer, Samsung tablet, Samsung camera, Dyson cordless vacuum cleaner, Black & Decker Dustbuster).

Entertainment devices on standby : Mixed results here. Our 19" digital LCD TV uses less than 1 watt on standby, whereas the recorder and DVD player use 6 and 7 watts respectively. So it's worth switching them off at the socket except when in use. Some people use TV power-down devices but switchable plugs seem fine for us.

Digital radios : We have three of these and they all have a power supply unit that plugs into the mains. The radios when switched on use between 5 and 9 watts. When switched off but still plugged into the mains, the power supply units feel warm and tick over at 2, 3 and 5 watts.

Calculation: If we left the 5 watt standby radio switched on at the mains plug and not in use for 21 hours a day (we typically have the radio on for 3 hours a day), how much energy would we waste in a year?

5 watts x 21 hours = 105 watt hours per day
105 watt hours / 1000 = 0.11 Kilowatt hours per day
0.11 KwH x 365 = 38.33 KwH per year (at 13p per unit, £4.98)

We did this in a spreadsheet for all our gadgets!