
The Kill-A-Watt Meter
You might be surprised to hear that electronic devices still consume power even when they’re turned off – pretty much anything that plugs into a wall outlet does. This power is referred to as “standby power,” and it’s commonly used to provide some sort of feature – like an infrared receiver listening for a remote, a computer waiting for the ON button to be pressed, or a DVD player displaying the current time. However, this standby load often provides no benefits at all.
Watts are used to measure the rate at which power is consumed, and power usage over time is usually measured (and billed for) in kilowatt hours (kW-h). The cost varies greatly depending on where you live, but the U.S. national average is about 12 cents per kW-h. In California, the average price for residential power is 15 cents and commercial power is one cent cheaper. The average American household (in 2007) consumed 936 kilowatt hours each month.
Although most power is used by appliances such as air conditioning systems and refrigerators, your electronics do consume a significant amount of power. But how much exactly? To answer that question, we’ve prepared the following table showing the typical power usage of computers, monitors, and peripherals.
| Off / Standby | Sleep | Not in Use | In Use | Peak |
| Desktop PC | 2 | 3-4 | 60-75 | 88-105 | 120 |
| Wide 19" LCD | 2 | 2 | 2 | 27 | 36 |
| Std 17" LCD | 1 | 1 | 1 | 25 | 36 |
| Small Laserjet | 1 | 4 | 4 | 835 | 835 |
| Laptop, 15" LCD | 4-5 | 5 | 31 | 45 | 70 |
| PC Speakers | 2 | N/A | 2-3 | 4 | 12 |
| 10/100 Switch | N/A | N/A | N/A | 3 | 3 |
| VoIP Phone | N/A | N/A | 2 | 2 | 2 |
So if your computer idles at 65 watts, then it would consume at least 46.8 kilowatt hours in a month (30 days) if you never turned it off. And if you live in California where power is 15 cents per kW-h, then you’d be adding $7.02 to your electric bill. Of course the cost will be a lot more depending on how much you use the monitor and peripherals, but at a minimum, your printer, monitor, switch, and phone will add another 14 watts for a total of 79 watts and $8.53.
Let’s say you wanted to lower expenses and you kept your computer and peripherals off at night by turning the power strip off (which stops almost all standby power usage). If your night is eight hours long, this would only save you $2.84 each month. However, if you shut down your computer and didn’t turn off the power strip – thereby losing some power – you would still save $2.27. The power lost at night due to standby power modes is only 57 cents in this case – not even worth considering.

A ''Stupid'' Strip
Even so, a few vendors are marketing “smart” power strips which can shut off some outlets when power usage on a control outlet gets low enough. So if your computer is on the control outlet and it goes to sleep, then the Smart Strip would turn off all power to peripherals on the other outlets. In our typical setup, these peripherals consumed only 14 watts of standby power, and even assuming the computer would be off or asleep for 15 hours each day, the most you could save in a month would be 95 cents. Hardly enough to justify the expense – both of money and energy – of a Smart Strip.