Last week we looked at the smart grid — essentially, a modernization of the transmission and distribution aspects of the electrical grid. This week we’re focusing upon tracking energy usage, since the first step to cutting down on our power consumption is being able to measure it. Smart meters installed as part of smart grid projects will make it extra-easy to monitor home energy use — and while there are numerous smart grid-linked energy monitoring devices coming out soon, there are also are plenty of ways to keep track of your power consumption with an old-fashioned meter.

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Before getting into individual products, it’s important to have a handle on how home energyuse is measured. Electric energy and natural gas consumption are measured in kilowatt-hours (power in kilowatts multiplied by time). The price of individual kWh varies depending on the time of day, but the devices below can help you estimate your power consumption costs.

One of our favorite energy-monitoring devices is P3’s Kill-a-Watt. It’s cheap ($20), and simple to use — just connect any electronic device to the Kill-a-Watt outlet and find out exactly how much power it’s consuming by the kWh. The Kill-a-Watt also lets you calculate energy expenses by the day, week, month and year, and they can even be rigged to tweet your power usage!

At $145, the Energy Detective requires a bit more of an investment than the Kill-a-Watt, but it’s also a more complex system. The Energy Detective consists of a Measuring Transmitting Unit that taps into your circuit breaker, a pair of Current Transformers that are clamped around power cables, and a Receiving Unit Display that plugs into a wall outlet and displays real-time power use by the kWh–much like the Kill-a-Watt system. Unlike the Kill-a-Watt, however, the Energy Detective displays energy information for the whole house.

Perhaps the most elegant power-monitoring device is Wattson, a $280 contraption that consists of a sensor hooked up to power cables along with a wireless receiver. A readout on top of the box shows power usage in either kWh or cash spent, but the device’s color-changing ability makes it easy to gauge your energy use from across the room. When power consumption is low, the box glows blue. When energy use is high, the box glows red, and if consumption is average, Wattson glows purple. It’s a simple, attractive way to keep an eye on energy.