A plug-in solar solution that utilities and lawmakers can agree on

Plug-in solar, also called balcony solar, lets homeowners and renters plug a small solar panel setup directly into a household outlet to generate their own power, without the permits, construction, or utility approval that a full rooftop system needs. Utah passed the first state law allowing this last year, and Colorado, Maine, Virginia, and others have since followed. This summer, California's Senate passed a bill 35-1, and New York and New Jersey passed their own, now waiting for their governors' signatures. In states with these laws, residents have saved between $175 and $340 a year on energy bills.

The debate now is over the technical limits these laws should set. Utah's law caps systems at 1,200 watts, a number borrowed from Germany's rules that doesn't quite fit American home wiring, according to the author, an industry executive. Without added safety controls, a system that size plugged into a regular outlet could overload household wiring and create a fire risk without tripping the breaker. He argues future state laws should instead allow smaller systems (up to 420 watts) to skip extra safety hardware, require added power-control equipment for bigger systems, and cap how much power a home can send back out to the grid at 400 watts, to ease utility concerns about grid reliability.

For homeowners, the takeaway is that these are state-by-state rules still being written, so what wattage, safety equipment, and savings apply depends on where you live and what your state ultimately passes.