Net metering vs. net billing: how solar exports change your savings
Separate electricity flows from bill credits, compare tariff structures, and work through examples showing why matching annual solar production to annual use does not guarantee a zero bill.
Sources reviewed: 2026-10-06
Key takeaways
- Solar consumed in your home and solar exported to the grid can have different financial values.
- Net metering and net billing describe families of tariff designs, not one nationwide set of rules.
- Credit rates, netting intervals, carryover, settlement, and charges must be checked for your actual utility account.
- Annual kWh balance is an energy comparison, not proof that imports and exports cancel in dollars.
Questions to ask about any export tariff
| Term | What to establish | Why it matters |
|---|---|---|
| Netting interval | When imports and exports are combined or priced | Annual totals may miss hourly differences |
| Export compensation | Current rate or calculation and effective date | Exports may not match avoided import value |
| Credit carryover | Units, expiry, and eligible bill components | A credit may not offset every charge |
| Settlement | Treatment of unused balances and account closure | A banked balance is not automatically cash |
| Program eligibility | Customer class, enrollment, and equipment changes | A neighbor's terms may not apply |
Start with three separate electricity flows
Solar generation first supplies simultaneous household demand in a typical behind-the-meter installation. Surplus can flow to the grid or into a compatible battery. When household demand exceeds the available solar and battery output, the utility supplies the shortfall. Generation, self-consumption, exports, and imports are therefore different quantities. The Department of Energy's homeowner guide explains that solar savings depend on household consumption, production, utility prices, and compensation for excess electricity, not simply the number of installed panels.
A utility meter usually records exchanges with the grid, not the full electricity production shown in the inverter app. For a no-battery illustration, if solar generates 30 kWh over a day and 12 kWh is used on site, exports are 18 kWh. If the home consumes 25 kWh in total, imports are 13 kWh. The accounting is 30 = 12 + 18 for generation and 25 = 12 + 13 for consumption. These are invented daily totals, not a forecast; interval timing determines the actual flows.
Keep generation, exports, and imports separate
- 30 kWh generated: Total solar output in the illustration.
- 12 kWh used directly: Solar coinciding with household demand; it appears in both energy balances.
- 18 kWh exported: Solar not consumed on site: 30 − 12.
- 13 kWh imported: Household demand not met by solar: 25 − 12.
Diagram sources: www.energy.gov, www.tampaelectric.com
What net metering means and what it does not
Net metering generally uses a tariff-defined relationship between exported and imported electricity to reduce billed consumption or provide credits. The details vary: the tariff might net kWh over a billing period, distinguish time-of-use periods, carry credits forward, and settle remaining surplus under a separate rule. DOE explicitly recommends checking local availability, eligible system size, customer type, rates, and credit design. Do not treat the phrase net metering as a guarantee that every charge disappears or that surplus is paid in cash at a retail rate.
A concrete local example is Tampa Electric's net-metering explanation. Its page describes delivered kWh minus received kWh for net energy billing, surplus kWh banked for later months, and a basic service charge. That establishes the treatment described for Tampa Electric, not for every Florida utility and not for another state's tariff. Annual handling of unused credits and the applicable agreement should be confirmed separately rather than extrapolated from a monthly carryover explanation.
How net billing differs
In a net-billing design, imports and exports are commonly accounted for separately in dollars, with export compensation determined by an export tariff rather than automatically matching the import price. A low export rate can make daytime self-consumption more valuable than producing additional surplus. The relationship can also change by season or hour. Labels alone are insufficient: read the current rate schedule and identify how the utility measures, prices, applies, and settles exports for your customer class and enrollment date.
SMUD's Solar and Storage Rate illustrates separate export compensation alongside the residential Time-of-Day rate. SMUD says export credits offset electricity usage charges and remaining credits carry to subsequent bills. It also identifies different treatment for legacy net-energy-metering accounts. SMUD is a community-owned utility with its own rules, so this example should not be substituted for PG&E, Southern California Edison, or another utility's tariff. Check the utility directory for the appropriate provider.
A worked energy-versus-money example
Consider a hypothetical month with 300 kWh imported and 300 kWh exported. Under a simplified one-for-one monthly kWh-netting design, the net energy quantity would be zero: 300 minus 300. Under a hypothetical separate-dollar design with imports priced at $0.30 per kWh and exports at $0.08, imports cost $90 and exports earn $24, leaving $66 in energy charges before other charges. The same physical energy balance produces different billing results. Neither rate is a real utility offer.
This comparison intentionally excludes tiers, hourly prices, taxes, minimum bills, and credit restrictions so the mechanism is easy to see. A real estimate needs those items restored. Annual solar production equal to annual household demand also does not prove that monthly or hourly quantities balance. For example, summer surplus may have a different settlement treatment from winter imports. Keep both the energy accounting and the tariff accounting in the model; do not multiply every generated kWh by a single retail price and call the result guaranteed savings.
Equal kWh can produce unequal dollar results
- Monthly kWh netting: 300 imported − 300 exported = 0 net kWh. Other charges can still remain.
- Separate dollar accounting: 300 × $0.30 = $90 imports; 300 × $0.08 = $24 exports; $66 energy balance remains.
Diagram sources: www.tampaelectric.com, www.smud.org
Self-consumption changes the value of a kWh
A solar kWh consumed as it is produced can avoid an import that would otherwise occur at that time. A solar kWh exported earns the tariff's permitted export value. This distinction is central when those values differ. In a hypothetical case with an avoidable $0.30 import charge and a $0.08 export credit, shifting a suitable 1 kWh household activity into surplus-solar hours could improve the gross energy result by $0.22, provided it truly replaces that import and does not create extra consumption.
That illustration is not a universal savings rule. Some bill components are not avoidable through self-consumption, a time-of-use period may have a different rate, and a shifted activity may change efficiency or comfort. Storage also introduces conversion losses and additional costs. Use the self-consumption and export estimator for an energy-flow starting point, not a utility-dollar valuation. Read the battery guide before assuming that storing every surplus kWh is financially worthwhile.
Credits, carryover, and settlement are separate questions
Identify whether the credit balance is stored in kWh or dollars, which charges it can offset, how long it carries over, and what happens at an annual settlement or account closure. A positive balance on the bill is not necessarily withdrawable cash. Some programs have different rules for carried credits versus final surplus payments. Ask the utility to explain an example statement with both a surplus month and a deficit month, using the rate code that will apply to your installation.
Also ask about the netting interval. Monthly totals can hide substantial imports and exports within the same day, while interval-based pricing can value them differently. If the tariff uses time-varying rates, obtain consumption data and a production profile that match the required billing intervals. A quote showing annual generation and an annual electric bill is not enough to reconstruct an hourly tariff. Verify how the provider treats daylight-saving changes, tariff changes, and a partial first billing period if those details affect its calculation.
Legacy programs, batteries, and system changes
A neighbor's export arrangement may differ from the one available to a new installation. Enrollment dates, legacy protection, expansions, ownership transfers, and storage incentives can change eligibility. SMUD's official page, for example, explains that legacy NEM and the newer Solar and Storage Rate coexist and that certain changes affect rate treatment. Before increasing an array, replacing equipment, adding storage, or buying a home with solar, ask the serving utility whether those actions require a new application or tariff transition.
Do not assume the whole state has one solar export rule. Utility ownership, regulator authority, supplier arrangements, and service territory can differ. In California, a municipal utility's program should not be modeled as if it were an investor-owned utility's program. In Texas, confirm the relevant utility and any electricity-provider buyback terms. These examples show why account-level evidence is more useful than a generic state-wide net-metering label.
How to verify a proposal's export assumptions
Request the utility name, rate code, customer class, program version, assumed enrollment date, import prices, export prices, carryover rules, and non-offsettable charges used in the savings model. Ask which values are current published terms and which are assumptions about future changes. Have the provider show both the solar energy split and the dollar bill calculation. If the proposal only says full retail credit, request the official source and the clause establishing which components and periods that statement covers.
Use the quote comparison checklist to record the assumptions consistently across installers. Review a state guide for context, then confirm your actual account with the utility's current tariff and interconnection agreement. The best export estimate does not promise that a policy will never change. It identifies today's applicable rules, dates the review, makes uncertain assumptions visible, and shows how savings would change if export value or household timing differs.
Frequently asked questions
Does net metering always pay the full retail rate?
No. Rate components, netting intervals, surplus settlement, and program versions differ. Check the actual tariff rather than interpreting the label as a nationwide guarantee.
Why can I owe money if annual solar equals annual consumption?
Timing and pricing can differ between imports and exports, and fixed or non-offsettable charges can remain. Equal annual kWh is not necessarily equal dollar value.
Is a credit balance the same as cash?
Not necessarily. The tariff determines what credits offset, whether they carry forward, and how remaining balances are settled.
Is net billing the same everywhere?
No. It is a general description of separate billing or credit treatment. Import prices, export formulas, periods, and charges remain utility-specific.
Does adding a battery guarantee better economics?
No. Compare avoided imports with forgone exports, losses, installed costs, and operating rules. Backup value is a separate consideration.
Can I use my neighbor's solar tariff?
Only if your account meets the same applicable eligibility and enrollment rules. Legacy program status and later system changes can produce different terms.