Net Energy Metering (NEM) is a solar incentive. It gives you the ability to send extra energy generated by your home solar panels back to the grid for a credit, which will be applied to your future electricity bills. With NEM billing, you only pay for your “net” energy usage.
For example, during the day your solar panels may generate more energy than you consume at that time. With NEM, you’ll earn credits for this excess energy. When your home energy consumption is greater than your solar system’s output, these credits will apply towards powering your home with energy from the grid.
It’s similar to rollover minutes—NEM allows you to “rollover” these energy credits to when you use more energy than your solar panels are generating and/or your Powerwall has stored.
Tesla’s solar power systems are grid-tied and will send excess solar energy to the grid when needed. This also applies to customers with Powerwall, who can take advantage of Net Energy Metering after their Powerwall units are full.
Please keep in mind that Net Energy Metering laws vary widely from state-to-state.