Charlie Stross breaks it down Mr. Wizard style:
So many electrical items around the home have little 'standby' LED lights these days. Indeed it's shocking how much energy they use as well (apparently around 90% of the power needed to run the appliance - so there's another 'saving money' issue for you!). Does everything in your house really need to be permanently on standby? Plugging and unplugging electrical items is the work of but a moment and can make a difference to the environemt and your bank balance!
Er, no. Just how much juice does a standby appliance consume, really, and how much would we save if everybody in the UK religiously turned off appliances they weren't using? Let's try and come up with some numbers.
The first point I'd like to note is that, contra the well-meaning assertions of Shropshire Green Party, devices in standby mode do not all consume 90% of their maximum power drain. Take the laser printer sitting on the other side of my office; it's rated power drain in standby is 11 watts, but when in operation, peak drain is around 700 watts. It's a few years old; modern appliances tend to be a lot more parsimonious with their standby draw. Ditto items like LCD televisions or VCRs and PVRs; newer ones tend to run on single-digit watts when in standby, primarily to keep the infrared receiver powered up (so that they can come fully to life when you hit the "go" button).
The next item on the green hit list is items like mobile phone, PDA, or iPod chargers — wall warts, those blocky transformers that everything seems to come with these days. They're often warm to the touch; doesn't this mean they're consuming lots of power? Well, no. You'd be surprised how little power it takes to keep a small transformer warm; a couple of watts will do it, over time, because they've got chunky lumps of metal inside that hold heat efficiently, and they don't get hot enough to dissipate it through air convection -- so contact with your hand is the most effective way of cooling them. Typically we're talking 2-5 watts. (If it was on the order of 100 watts, you'd know about it — you'd burn your hand as soon as you touched the thing, just like a halogen spotlight.)