A solar proposal needs a verified billing rule for the actual customer account. “Net metering available” is not enough to establish the value of exports, the size allowed or when the customer may operate the system.
This reference is for installers building a tariff record, comparing designs and handing over a grid-connected system. It uses selected official examples checked on 30 September 2026. It is not a complete current policy table for every state and country; tariff eligibility and technical requirements still need project-specific confirmation.
Answer: what to verify before quoting
For a solar quote, verify how the actual tariff measures imports and exports, values exported energy, carries or settles credits, and treats fees and eligibility. Net metering and net billing labels do not establish every billing rule. Model the customer’s load and production using those terms, then track utility approval separately from the savings estimate.
Start with the energy flows
For a conventional behind-the-meter solar installation without storage, production can serve onsite consumption or flow outward as exports. Grid imports supply consumption not served by contemporaneous solar. A bill may value these flows differently.
| Flow | Meaning | Financial question |
|---|---|---|
| Solar used onsite | Generation serving the customer’s load | Which import charges does it actually avoid? |
| Export | Energy sent through the connection to the network | Which credit/payment rate and conditions apply? |
| Import | Energy purchased from the network | Which energy, demand and other charges apply? |
| Stored energy | Energy charged into and later discharged from storage | What are the losses, source restrictions and permitted operating modes? |
An import/export meter is not necessarily a gross-generation meter. Its export register does not include solar already consumed behind the meter. With storage, use an energy balance that also accounts for charge, discharge, losses and any grid charging.
Net metering, net billing and feed-in arrangements
Net metering often involves energy netting or credits tied to a consumption tariff. Net billing commonly measures purchases and exports separately and applies an export value. A feed-in or export-payment contract may pay for exported electricity, while some arrangements also remunerate gross generation.
These descriptions are starting points. The governing tariff determines the interval, price, eligible charges and settlement. Avoid defining every net-metering program as a full-retail payment or every export tariff as a fixed rate below retail.
Also distinguish a bill credit from a cash payment. A credit that can offset only specified bill components is not equivalent to unrestricted cash income.
Build a tariff record for each customer
Keep a dated source file, not just a number entered in the proposal template.
| Record field | What to establish |
|---|---|
| Utility and service area | Actual network/supply company for the address |
| Customer class and import schedule | Residential/business status, rate plan and metering basis |
| Export rider or contract | Current document, effective date and customer-specific cohort |
| Eligibility | Technology, size basis, customer/account conditions and allowed configuration |
| Import/export measurement | Interval and treatment of simultaneous or separate registers |
| Export value | Fixed, time-varying or otherwise calculated; applicable additions |
| Credit settlement | Rollover, true-up, expiry, payout and eligible charges |
| Charges | Fixed, minimum, demand, metering, application and relevant recurring charges |
| Legacy conditions | Trigger date, duration, transfer and modification provisions |
| Technical approval | Capacity/export limit, interconnection, required evidence and operating permission |
Different caps answer different questions. A DC module rating, inverter AC rating, apparent-power limit, export limit and program capacity are not interchangeable. Record which quantity the actual condition uses.
Use regulator and utility sources to resolve conflicts. A database or industry guide can help locate a program, but a summary is not a substitute for the applicable current tariff and agreement. If the relevant document is unavailable, mark the assumption provisional and get confirmation before promising a benefit.
Arizona example: APS has different renewable riders
For net billing in Arizona, begin with the utility and customer class. A single state export price does not establish the applicable tariff.
APS’s official renewable-energy rider page describes RCP as a residential net-billing solar purchase rider. It separately describes EPR-2 net billing and business/legacy net-metering riders. Their eligibility and settlement conditions differ.
For an APS quote, identify the permitted rider, the actual purchase-rate document and customer cohort. Record rollover and settlement conditions from that document. Do not infer that every Arizona customer receives one export rate, or that every application automatically locks the same terms at energization.
APS’s rooftop-solar workflow also separates interconnection approval for installation from the later inspection, metering and permission-to-operate step. A savings forecast should not show the system operating before its authorized start merely because equipment has been delivered.
California example: use the applicable NEM or NBT cohort
The CPUC’s current NEM/NBT explanation distinguishes legacy NEM from the Net Billing Tariff for the regulated investor-owned utility programs. NBT applies to relevant interconnection applications from 15 April 2023. The utility-specific tariff and customer circumstances still matter.
The CPUC explains that NBT export values are usually below import rates but can exceed them at particular late-summer evening times. That makes a universal “all exports are always worth less” statement inaccurate. Model the applicable time-varying values and import schedule.
Do not promise a standard 75% loss of export value, fixed payback extension or mandatory economic benefit from a battery for every customer. Compare the proposed configuration using actual inputs. Municipal utilities and other California service arrangements should be checked under their own rules.
International examples: the program name is not the price
Philippines: Meralco Net-Metering
Meralco’s published billing FAQ explains that export credits use its monthly blended generation charge, excluding other generation adjustments. That is not the customer’s complete retail electricity rate, even though the program is called Net-Metering.
Use this as a terminology example. The Meralco application guide addresses the local pathway; its capacity, documentary and operating requirements should not be imported into an Arizona or European project.
Great Britain: SEG supplier terms
Ofgem’s Smart Export Guarantee guidance explains that participating suppliers choose their rate, contract length and relevant terms, subject to the scheme’s requirements. SEG-compliant tariffs must remain above zero.
There is no single national export price to insert into every quote. Establish customer eligibility and the chosen supplier’s actual contract; export payment and network-connection permission are separate matters. Do not generalize Great Britain’s scheme to every UK jurisdiction or treat legacy FIT and a new export contract as interchangeable.
Model settlement before optimizing system size
Retain the existing guide’s useful principle: use the customer’s actual load profile where suitable data are available. Match production, imports and exports to the tariff’s required interval and time zone. Document how you handled missing intervals and seasonal demand.
For a simple no-storage, instantaneous-separation example:
- Onsite use is the smaller of generation and load in each interval.
- Export is positive generation remaining after onsite use.
- Import is positive load remaining after onsite use.
Apply the applicable settlement rules after calculating those flows. If the tariff nets over a different period, follow that method rather than imposing this illustrative separation on it.
Then calculate the bill with solar and compare it with the relevant without-solar bill. Include charges that remain. A demand charge requires its actual measurement rule; it cannot be calculated by multiplying annual kWh by a blended energy rate.
Hypothetical example: export value changes the result
Assume one billing period has 500 kWh of generation, of which 300 kWh serves onsite load and 200 kWh is exported. For this example only, assume an avoided marginal import value of $0.30/kWh and an export value of $0.05/kWh:
| Component | Illustrative arithmetic | Value |
|---|---|---|
| Onsite-use benefit | 300 kWh × $0.30/kWh | $90 |
| Export credit | 200 kWh × $0.05/kWh | $10 |
| Combined energy benefit | $90 + $10 | $100 |
Valuing all 500 kWh at $0.30 would produce $150 and overstate this example’s energy benefit by $50. The numbers are invented for explanation, not an APS, California or Meralco tariff. Fees, taxes, demand charges, finance and storage are excluded, so this is not a complete savings or payback calculation.
Compare sizing and storage without a universal target
Evaluate realistic candidate layouts and, where relevant, storage cases. Compare incremental production and its timing, cost, export restrictions, self-consumption and settlement. A system producing 100% of annual consumption can still leave substantial imports and exports at different times.
A lower export value can increase the benefit of shifting consumption or storing energy, but the additional equipment has costs and losses. Include storage capacity, efficiency, controls, degradation, replacement assumptions and any charging/export restrictions. Separate resilience benefits from bill-saving estimates.
Do not prescribe “60–80% of load” as the optimal system size or claim oversizing always destroys ROI. The preferred configuration depends on the actual customer and constraints. Likewise, do not maximize module count merely because a program allows more capacity.
Legacy terms, credit expiry and later changes
Check the actual triggering event and conditions for any legacy treatment. The accepted application date, installation deadline, interconnection date or another event may matter. A policy proposal does not necessarily establish an effective tariff change.
Before expanding an existing installation, changing equipment, adding storage or transferring ownership, check whether the modification affects eligibility or legacy terms. Keep the customer informed about verified conditions without manufacturing urgency.
Record whether credits carry to another month, settle annually, expire or convert to cash under conditions. A retail-valued monthly credit does not imply retail compensation for all annual surplus.
Installer handover checklist
- Utility, class, import schedule and export arrangement identified.
- Current tariff/contract source and customer-specific eligibility recorded.
- Capacity and export restrictions use the correct rating basis.
- Import/export interval, credit settlement and residual charges modeled.
- Production/load assumptions and limitations disclosed.
- Solar-only and storage cases compared where appropriate.
- Permit, inspection, connection, metering and operating statuses tracked separately.
- Customer receives the applicable agreement, operating records and forecast assumptions.
- Actual bills checked against the model after authorized operation.
For the application workflow, see solar interconnection documentation. If evaluating SurgePV’s generation and financial workflow, bring the actual tariff, interval data and scenario requirements to a demo. Verify the applicable model inputs and outputs before relying on them; no automatic tariff coverage or savings guarantee is asserted here.
Frequently asked questions
Does net metering always pay the full retail rate?
No. Terminology and settlement rules vary. Check the actual tariff, including netting interval, eligible bill components and surplus settlement. Meralco’s program is called Net-Metering but its published export-credit basis is the monthly blended generation charge, excluding other generation adjustments.
How should an installer check net billing in Arizona?
Identify the utility and customer class first. APS publishes distinct renewable riders, including residential RCP and EPR-2 net-billing arrangements with their own eligibility and credit rules. Use the applicable current rider and interconnection conditions; do not apply an APS rate to all Arizona customers.
Does annual solar generation equal annual bill savings?
No. Energy used onsite, energy exported and remaining grid imports can have different values. Apply the actual measurement intervals, rate schedules and credit rules, and include charges that solar does not avoid. Annual energy balance alone does not establish a zero bill.
Does net billing automatically make a battery economical?
No. Compare the battery’s installed cost, usable capacity, efficiency, controls, degradation and replacement assumptions against the applicable import/export rates and load profile. Backup value and bill savings are separate benefits, and export or grid-charging permissions may constrain operation.
Do export credits expire or pay out in cash?
It depends on the applicable tariff and contract. Record rollover, settlement date, eligible charges, expiry and any cash-payment conditions separately. A monthly credit and an annual surplus settlement are not necessarily valued or treated the same way.
Is permit approval permission to operate?
Not necessarily. Track the applicable local inspection, utility connection, metering and operating authorization separately. APS’s published rooftop-solar workflow, for example, distinguishes installation approval from the later inspection, meter installation and permission-to-operate milestone.
Where this fits
This article is part of SurgePV's Solar Incentives & Policy hub, which works through the topic from first principles to the decisions a project team actually has to make.
