Net metering allows customers to generate their own electricity from solar power, small wind turbines, or small-scale hydro. A net meter, provided by NorthWestern Energy, is needed to measure the energy produced and consumed during the billing period. The electricity is used by the customer. They have batteries or capacitors that they charge as part of their normal operation for. A building permit is required for windmills, and additional permits, such as electrical permits for electricity-generating systems, may be necessary. Adding a wind turbine, solar.