Note the Black and Decker is the same as the original PowerCost Monitor.  It was being brand labeled by Black and Decker but it does not look like that is the case anymore.  Below is the review of the PowerCost Monitor, which also applies to the Black and Decker Power Monitor:

One of the complaints mentioned on Amazon is that the device that mounts on the outside of your electrical meter uses batteries, and sometimes these batteries do not perform well when exposed to the elements (rain or extreme cold). If you need to do net metering (i.e. measure energy consumed and produced by a solar PV or wind turbine), you will have to go with another energy monitor.

Keep in mind that the sensor unit that mounts on your electrical meter on the outside of your home will have to be within 100' of the display unit.

Note that the Black and Decker Power Monitor is made by Blue Line and will work with the WiFi Gateway as well. The Black and Decker units are usually cheaper than the PCM on Amazon but that is because they are no longer being supported by Black and Decker.

The following comes from our blog post on Installing the PowerCost Monitor WiFi Edition (note that references to Microsoft Hohm and Google PowerMeter are now invalid as those services have shut down.  Instead, check out myEragy, PlotWatt, and People Power are home energy web services that support the PowerCost Monitor with WiFi Bridge):

"One of the nicest features of this product is the ease of installation requiring very little effort and no onsite visit from an electrician. (or risk in taking the cover off of your circuit panel box yourself)  The PowerCost Monitor (PCM) consists of two components: the display unit and the sensor unit.  Both run on AA batteries.  After one look through the directions, installing the sensor unit was very straightforward.  Positioning the sensor arm and eye is the same on all analog power meters with the spinning wheel.  The eye is positioned over the center of the wheel and reads the notch each time it passes under the eye.

If you have a smartmeter, you should first write down your smartmeter brand and model and look it up on BlueLine Innovations (BLI) website in their customer support section.  It has most of the popular smartmeter brands with pictures of where to position the eye of the sensor unit.  The first time I set it up I made an assumption of where I thought the eye was located and was wrong and it didn’t pick up a signal.  After I saw the picture of my smartmeter with the arrow pointing to the correct location, I moved it to the right position and it worked right away!

Configuring the display unit requires entering a few values into the configuration screen such as the time, date, utility rate and Power Factor.  The instructions were very easy to follow.   Once the sensor unit was in place, you press the Sync button on the display unit and watch your live energy usage on the screen!

Installing the Wifi Gateway

The PCM Wifi Gateway is a small plastic donut-shaped object that receives the signal from the sensor unit and broadcasts the data through your wifi router to either Microsoft Hohm or Google Powermeter.  Once it is configured, it does not require a direct connection to your computer.  You can place it close to a wall near the sensor unit, within range of your wifi network and near a plug since it does require 120v AC power to operate.

To configure the gateway, install the software, plug the donut into your computer with the usb cable provided and enter your wireless network information into the configuration screens.  Once it’s configured, unplug the cable and position the donut to the wall nearest to your smartmeter and plug it into an outlet.
You’re done."