You see your neighbor’s electric meter running backward and want in. But before diving in, it’s important to understand: net energy metering doesn’t open the doors for every shiny, spinning gadget that kicks out electrons. There are definite rules and a few interesting wrinkles.

First up, the A-listers: Solar photovoltaic (PV) systems. These are the number one ticket for net metering programs across the U.S. The humble yet powerful PV panel is everywhere from handmade shed roofs in Vermont to mansions in Malibu. As long as you’re grid-tied, you’re most likely eligible. No grid connection? Sorry, you’re left out in the cold.

But solar doesn’t hog the spotlight. Wind turbines, even the little “backyard pinwheels,” often make the cut if you have a decent breeze and a system that plays nice with your utility’s voltage. Some folks, especially in Midwest states, get mileage out of small-scale wind projects—one or two turbines whistling away on the property.

Hydroelectric also slips onto the guest list. If you’ve got a creek or a steady stream, micro-hydro generators can qualify for many net metering programs, though probably not many city folks can set one up out back. The story’s similar for biomass and fuel cell systems. In rare cases, household-scale “anaerobic digesters” or fuel cells that create electricity from natural gas, hydrogen, or biogas find themselves inked into the program, especially in states like California and New York.

Utilities set size limits. Most states keep residential systems between 10 kW and 25 kW—plenty for most homes. Commercial and agricultural users might tap out at 2 megawatts (MW) or more, depending on local rules. No sense trying to sell a small power station’s output back on a residential meter.

Any system qualified for net metering must meet safety standards. We’re talking certified inverters, approved disconnect switches, and grid-compatibility testing. Your electric utility will demand a professional installation and a safety inspection. You can’t slap together an abomination of solar panels and hope to get paid.

Some programs now allow “community solar.” You can subscribe to a shared solar farm and reap credits, even if your apartment is shaded by oak trees and pigeon nests. These setups can be a golden ticket for renters and condo dwellers.

Let’s not forget—rules vary by state, and even by utility. Hawaii, for instance, closed off net metering for new applicants and moved to “grid supply” programs instead. Other states, like Minnesota and Massachusetts, embrace broader system types and higher size caps.

So, before you cash in on sunshine or wind, chat with your utility or local solar pro. It’s not exactly a “one size fits all” party. Get your homework done, and you could soon be waving goodbye to high bills, with the sun (or wind, or water, or, for the truly adventurous, cows) working for you.