Review: 3 power plug meters help you save money and energy

Computerworld - With the ever-rising cost of electricity, we're all getting increasingly sensitive about how much power our computers, televisions, appliances and other doohickeys are using -- not just when we're using them, but also when they're allegedly turned off.

Some, like refrigerators, aren't running full tilt all the time. Others, such as computers, printers, displays and other gear, have "sleep" modes -- they power down significantly but they're still on. And some devices, like televisions and cable boxes, aren't really off when we push that "Off" button or switch. All are still drawing a small amount of power, a phenomenon that's called "parasitic load."

So how do you measure how much power you're actually losing to this load?

For home users, the electric meter outside the house shows how much total power is being consumed, but trying to watch that meter for changes when flipping the appliance on and off is challenging at best. If you're running an IT computer room or a data center, there are the new Power Distribution Units, like Raritan's Dominion PX family of devices, that can monitor power consumption down to the outlet level and toggle power to outlets individually. But devices like the 20-outlet, $1,249 Dominion PX are outside the budget (and needs) of a consumer.

Your alternative: a power plug meter, also called a "plug load meter."

A power plug meter sits in between the power outlet and an individual device and displays how much power (load) the connected device is consuming at the moment. It can track power consumption during a connected session, and calculate kilowatts and dollars per day, week, month or year. This function is important because, unlike something as simple as a light bulb, which operates for a set amount of time and always uses the same amount of power, many of our electrical and electronic devices use varying amounts of power.

Today's power plug meters can also track the minimum and maximum power draw in a session. Some even show the line voltage and monitor and track other aspects of power quality -- helpful in diagnosing problems and determining where you may need power protection accessories.

A power plug meter also should be able to tell you the device's power factor, which is calculated using factors such as the capacity of the circuit, and its current and voltage -- and is what your electric company uses to determine how much you're going to be charged.

Having all this information can help you decide whether it's worth turning off or unplugging your TV, desktop or cordless phone when it's not in use -- or whether your current device is a power pig and should be replaced.

To test how well power plug meters work, and whether they can really help save power (and money), I looked at three devices: P3 International's Kill A Watt EZ, Electronic Educational Devices' Watts up? Pro and Brultech Research's Energy Consumption Monitor/Logger ECM-1220.

All three devices measure 100-volt AC devices (i.e., anything you would plug into a wall socket in the U.S.), and two of the three can also measure 240-volt appliances like electric stoves and dryers. They offer basic information such as current power draw in amps or watts, session cost and monthly cost. They also provide tech/diagnostic data like minimum and maximum power draw; and all three measure the power factor.

Which power plug meter should you buy? Here are my thoughts.