The SENS House started with a 1440-watt grid-intertied solar tracking photovoltaic array to provide a portion of the house’s electricity usage. Over about 5 academic years, around 55% of total house electric use has been provided by the array.
In the fall of 2011, a fixed, 3150 watt array was installed on the roof. Combined with the tracking array, this makes the house “net-zero”–in other words, while it is still tied to the grid and can buy and sell electricity as needed, all of the house’s electricity usage is offset over the course of the year by its photovoltaic panels. The house produces as much electricity as it uses–and possibly even more.