How Solar Net Metering Works: Credit Rollover, True-Up Billing & NEM 3.0 Rate Changes Explained
What Is Solar Net Metering?
Net metering is a billing arrangement between residential solar panel owners and their electric utility. When your rooftop solar system generates more electricity than your home uses at any given moment, the surplus energy flows back into the grid. Your utility meter literally spins backward (or registers a negative reading on a digital meter), giving you a credit on your electricity bill for the power you exported. Later—at night or on cloudy days—when your panels aren’t producing enough, you draw electricity from the grid and use up those credits before paying out of pocket. For homeowners, net metering is the single most important policy that makes rooftop solar financially viable. Understanding the credit mechanics, billing cycles, and the major changes introduced under NEM 3.0 in California can save you thousands of dollars over the lifetime of your system.
How Net Metering Credits Work
The core concept is straightforward: every kilowatt-hour (kWh) you export to the grid earns you a credit, and every kWh you import from the grid costs you. At the end of a billing period, the utility calculates the net difference.
- Net surplus in a month: If you exported more than you imported, the excess credits roll over to the next billing period.- Net deficit in a month: If you imported more than you exported, your rolled-over credits are applied first. You only pay for any remaining balance.- Minimum charges: Even if your credits fully offset your consumption, most utilities still charge a small monthly minimum delivery or connection fee, typically between $10 and $15.
Credit Rollover Rules
Monthly Rollover
Under traditional net metering (often called NEM 1.0 or NEM 2.0), excess credits generated in any billing month automatically roll forward to the next month. This is essential because solar production is seasonal: your panels produce far more energy in summer than in winter. The credits you accumulate during long, sunny days in June and July carry forward to cover your higher net usage in December and January.
Annual Rollover and Net Surplus Compensation
Credits continue rolling over month to month throughout your annual billing cycle—typically a 12-month period. At the end of that cycle, if you still have unused credits remaining, the utility pays you for that net surplus. However, the compensation rate for this annual surplus is almost always lower than the retail rate. In California under NEM 2.0, for example, net surplus compensation was approximately $0.02–$0.04 per kWh—far less than the $0.30+ retail rate. This is a strong incentive to size your system to match your annual consumption rather than significantly overproducing.
True-Up Billing Cycles Explained
The true-up statement is the annual reconciliation of your solar energy account. Here is how it works in practice:
- Your utility sets a 12-month billing cycle starting from the date your solar system receives Permission to Operate (PTO).- Each month, the utility tracks your energy imports, exports, and the monetary value of each. You receive a monthly statement showing activity but typically only owe non-bypassable charges and minimum delivery fees.- At the 12-month mark, the utility issues a true-up statement. This is the final accounting. All accumulated charges from months where you used more than you produced, minus all accumulated credits from months where you produced more, result in a single net amount.- You pay the balance (if any) on the true-up statement. If your credits exceeded your charges, you receive net surplus compensation at the wholesale rate.Planning tip: Review your monthly statements throughout the year so your true-up bill doesn’t surprise you. Many homeowners are caught off guard when their first true-up arrives with a balance of several hundred dollars because their system was slightly undersized or their consumption increased.
NEM 3.0: What Changed and Why It Matters
California’s Net Billing Tariff, commonly called NEM 3.0, took effect on April 15, 2023, and fundamentally changed the economics of residential solar. Here are the critical differences:
| Feature | NEM 2.0 | NEM 3.0 (Net Billing) |
|---|---|---|
| Export credit value | Near-retail rate (~$0.25–$0.35/kWh) | Avoided Cost Calculator rate (~$0.04–$0.08/kWh avg.) |
| Credit calculation | Fixed by rate schedule | Varies hourly based on time-of-use and grid value |
| Monthly rollover | kWh credits roll over at retail value | Dollar credits roll over (not kWh) |
| True-up cycle | Annual | Monthly billing with annual true-up |
| Battery incentive | Minimal financial benefit | Strong incentive to self-consume and store energy |
| Non-bypassable charges | ~$0.02–$0.03/kWh on imports | ~$0.02–$0.03/kWh on imports (unchanged) |
What This Means for Homeowners
Under NEM 3.0, the strategy shifts dramatically toward self-consumption. Maximizing the electricity you use directly from your panels—rather than exporting it—is now the fastest path to return on investment. Battery storage systems like the Tesla Powerwall or Enphase IQ Battery become near-essential add-ons. By storing midday surplus and using it during expensive evening peak hours, you effectively earn the full retail rate on that energy instead of the reduced export rate. Homeowners who installed solar under NEM 1.0 or NEM 2.0 are grandfathered under their original tariff for 20 years from their PTO date. NEM 3.0 applies only to systems that received PTO on or after April 15, 2023.
Tips for Maximizing Your Net Metering Benefits
- Size your system correctly. Aim for 100–110% of your annual consumption under NEM 2.0. Under NEM 3.0, slightly undersizing and adding a battery may yield better economics.- Shift consumption to solar hours. Run dishwashers, laundry, EV chargers, and pool pumps during midday when your panels produce the most power.- Add battery storage under NEM 3.0. Storing 10–15 kWh of midday production for evening use can save $50–$100 per month compared to exporting at low ACC rates.- Monitor your system monthly. Use your utility portal or solar monitoring app to ensure production matches projections and catch any system issues early.- Understand your rate schedule. Time-of-use (TOU) rates mean some hours are far more expensive than others. Align your consumption and battery dispatch with your specific TOU plan.
Frequently Asked Questions
Do my net metering credits expire?
Credits roll over month to month throughout your annual billing cycle and do not expire during that period. At the annual true-up, any remaining surplus credits are paid out at the net surplus compensation rate—typically a wholesale rate far below retail. Under NEM 2.0, this is approximately $0.02–$0.04/kWh. Under NEM 3.0, the dollar credits roll over monthly and are reconciled at the annual true-up in a similar fashion.
Can I switch from NEM 2.0 to NEM 3.0 or vice versa?
If you are grandfathered under NEM 1.0 or NEM 2.0, you remain on that tariff for 20 years from your PTO date. You cannot voluntarily switch to NEM 3.0 and then switch back. However, if you significantly modify your system—such as increasing panel capacity beyond a certain threshold—you may be required to transition to the current tariff. Always consult your utility before making system changes.
Is solar still worth it under NEM 3.0?
Yes, but the payback period has lengthened. Under NEM 2.0, typical payback periods were 5–7 years. Under NEM 3.0 without a battery, payback extends to 9–12 years. However, pairing solar with battery storage can bring the payback period back down to 6–8 years by maximizing self-consumption and avoiding expensive peak-hour grid electricity. Federal tax credits (currently 30% under the Inflation Reduction Act through 2032) and potential state incentives further improve the economics.