New entrants include Opower, Coulomb Technologies, Grid Net and Tendril Networks.

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"There's a desire to step out of the rat race, and in America, that goes very deep in the national psyche, " says Nick Rosen, author of "Off the Grid: Inside the Movement for More Space, Less Government, and True Independence in Modern America" and editor of www.off-grid.net.

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His system has a design that makes it easier to get the air through it, uses cheaper materials and does not draw electricity from the grid, which adds to costs and reduces the net amount of carbon stored (since grid electricity comes with carbon emissions attached, from the fuel used to make it).

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When they start using their own clean energy sources what will the net decrease (or increase) of CO2e be compared to using grid power?

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Ohio, was built to be a net zero energy building, but it still needed to pull energy from the grid for 11 years.

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Main.net's system skips the high-voltage lines, injecting data into the grid further downstream, on medium-voltage (4, 000 to 25, 000 volts) lines.

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