In addition to energy generated by large facilities, Massachusetts also allows excess energy generated by small-scale, distributed systems to be purchased by utilities (for up to 3% of their peak load) and fed back into the grid. This is known as “net metering.” When the system owner is consuming energy, their electricity meter spins forward. When they are producing energy for the grid, the meter spins backward. At the end of the month, they are only charged for their net energy consumption (their total consumption minus their energy production). If they produce more energy than they consume in a given billing period, they will receive credit for the excess energy they produced but did not use. Read more.