How Net Metering Works (and Why Your Rate Might Not Be What You Think)

Net metering is the arrangement that makes grid-tied solar pencil out for most homeowners: when your panels produce more than your house is using — the middle of a sunny day while you're at work — the excess flows backward through your meter and onto the grid, and your utility credits you for it. When your panels aren't producing enough (night, a cloudy stretch), you draw from the grid as normal and those credits offset the bill. The U.S. Energy Information Administration defines it simply as a billing arrangement that lets a customer's own generation reduce the electricity they're billed for over a billing period — the mechanics of exactly how that credit is calculated is where it gets complicated, and where it varies by state.

The basic mechanism

1. Your utility installs a bidirectional meter (or a smart meter that already tracks both directions) when your solar system is connected.
2. During the billing period, the meter nets your consumption against your export: draw 900 kWh from the grid, send back 400 kWh, and you're billed for the 500 kWh difference.
3. Under traditional net metering, that exported kWh is credited at the same retail rate you'd pay to buy it — a straight 1:1 swap.
4. Unused credits typically roll over to the next billing period (rules vary — some expire, some carry over indefinitely, some get paid out in cash once a year at a lower wholesale rate).

"Net metering" and "net billing" aren't the same thing anymore

The 1:1 retail-rate version above is true net metering, and it's what made solar's payback math simple for the last two decades. The newer trend — led by California's NEM 3.0, officially a "net billing tariff" — credits exported power at something closer to the utility's avoided cost (roughly what it would have paid a wholesale power plant for that electricity) instead of the retail rate. In California that dropped the export credit from around 30¢/kWh under the old rules to roughly 5-8¢/kWh under NEM 3.0. The math still works with a home battery in the mix — store the midday excess and use it yourself in the evening instead of selling it cheap and buying it back expensive — which is exactly why NEM 3.0 triggered a surge in battery attachment rates alongside new California solar installs.

It still varies enormously by state

Roughly 38 states plus Washington D.C. have some form of net metering or net billing on the books, but "some form" is doing a lot of work in that sentence — system size caps, rollover rules, and whether credits ever expire all differ by state and sometimes by individual utility within a state. States that consistently rank well for homeowners — Massachusetts, New Jersey, Maryland, Vermont, and Oregon among them — tend to share three traits: full retail-rate credit, credits that roll over for a full 12 months (so a big summer surplus can still offset a high winter heating bill), and no restrictively small system-size cap.

Grandfathering: why the interconnection date matters

When a state changes its net metering rules, it almost always protects customers who were already interconnected before the change — California grandfathers pre-April-2023 NEM 2.0 customers for a full 20 years, for example. That's a real incentive to lock in current rules sooner rather than later if a policy change is being debated in your state, since the terms you connect under are usually the terms you keep for the life of the incentive, not the terms in effect when your panels eventually wear out.

What this means for sizing your system

Under strong 1:1 net metering, there's less financial harm in sizing panels a bit larger than your own daytime usage, since excess export is worth full retail credit anyway. Under a net-billing structure with low export rates, the better financial target is sizing panels closer to your own daytime consumption plus a battery to shift the rest to evening use — the incentive shifts from "sell everything you don't use" to "use everything you produce, one way or another." Our solar and backup-plan calculators size for your actual appliance load either way — check your utility's specific export rate before deciding whether to lean the system bigger or add storage.