Wisconsin utility regulators have approved changes in net-metering rules proposed by the state's largest electric utility that will lower the compensation for excess electricity sold to the grid, and change bookkeeping rules so homeowners with photovoltaic (PV) Generation of electricity directly from sunlight. A photovoltaic cell has no moving parts; electrons are energized by sunlight and result in current flow. (PV Photovoltaics. Generation of electricity directly from sunlight. A photovoltaic (PV) cell has no moving parts; electrons are energized by sunlight and result in current flow. ) and wind systems can't carry solar credits for more than a month. We Energies says the new rate structure spreads the costs of maintaining the grid more evenly. Solar advocates say the changes will dampen interest in renewable energy. In reporting on that and other recent rate cases, Mi...