Looked at one way, the SunPort power outlet is an unnecessary product. The device itself, after all, doesn't actually reduce your energy use, but instead simply lets you offset your usage by buying solar credits -- something you can do without a dedicated device.
As the company behind it explained to Fast Company, however, they think that by automating the process, and making it more visible in the form of a plug, they'll be able to get more people onboard with solar offsets than would otherwise sign up for them on their own.
And, indeed, the device does have its own advantages. In addition to calculating how much energy you use and automatically purchasing credits (through ReChoice, a non-profit organization), it lets you keep track of that energy use to see exactly how much each of your electronic devices have been using. Something that could potentially encourage folks to cut back some on their electricity use by turning off particularly big energy draws when they're not in use. The company also says that the offset cost is smaller than many people may think, with something like a laptop running in the range of $1-2 per month.
As you might have guessed, the device is headed to Kickstarter for its launch, which is set for July 28th. And you'll need to wait for it if you're interested in the actual cost of the device -- right now, SunPort is only saying that it will be "affordable."
