Imagine the simplest possible metering arrangement: a single, 1960s-standard electromechanical meter. Now imagine that a residential customer, Ray McSolar, added a rooftop photovoltaic (PV) system (also known as a solar-electric system) to his home, on his side of this meter. Ray wakes up early for his job; on most days, he is out of the house before sunrise. In these dark morning hours, Ray makes his coffee and breakfast while watching the morning news on TV. The electric meter spins forward as Ray is consuming electricity from the grid.
Determined not to waste a bit of electricity, Ray shuts off all of his appliances as he heads off to work. Ray’s solar panels now start churning out electricity as the sun rises—electricity Ray sends back to the overstressed grid. His meter now spins in reverse.
When Ray returns at night to cook dinner and relax in front of the TV, the meter spins forward again as he consumes more electricity than his system generates. The result?
Ray’s bill will show only his net consumption of electricity from the grid. Should it be a hot sunny month (when the grid needs the most help), or a month in which Ray’s electricity use is low, any excess electricity his system generates is rolled over to his next bill, just as he might rollover excess cell phone minutes.
Net metering allows for the production of electricity that reduces demand on a strained grid. For the utility, this is exactly the same result as if Ray had installed a more efficient refrigerator. The only way his utility would know the difference between the use of more efficient technologies (such as an Energy Star refrigerator) and the use of customer-sited DG (such as a PV system) is if the utility installed a costly additional meter at Ray’s home and undertook the burden and expense of reading both meters and billing Ray for the result of this process.
In effect, net metering a simple billing arrangement for customer-sited DG. Without exception, significant deployment of clean, customer-sited DG occurs only in states with modern interconnection and net metering policies.
When Ray returns at night to cook dinner and relax in front of the TV, the meter spins forward again as he consumes more electricity than his system generates. The result?
Ray’s bill will show only his net consumption of electricity from the grid. Should it be a hot sunny month (when the grid needs the most help), or a month in which Ray’s electricity use is low, any excess electricity his system generates is rolled over to his next bill, just as he might rollover excess cell phone minutes.
