Net Metering Savings: Calculator Inputs and Bill-Credit Rules

Answer: A net-metering savings estimate needs the customer’s consumption, modeled solar production and the applicable utility tariff. Separate electricity used on site from exported surplus and later grid imports. Check how credits are valued, carried forward and settled. A calculator result is a scenario based on those inputs; it does not establish a universal savings percentage or eligibility for a programme.

Start with the actual electricity agreement

A savings calculator is useful only when its inputs match the customer’s project. DOE’s homeowner solar guide identifies service-area availability, eligible system size, customer type, rates and bill-credit design as questions to check. A state name alone does not determine the customer’s tariff.

Retain the utility, service territory, customer category, tariff identifier, enrollment date and export agreement. Existing and new customers may have different arrangements. Confirm the applicable programme before using an advertised export rate or assuming that eligibility transfers to a new owner.

This guide explains how to examine an estimate. It does not present an independently verified nationwide ranking of current tariffs or a universal percentage of solar value recovered.

Net metering and net billing need different inputs

The CPUC’s net-energy-metering and net-billing comparison distinguishes import-rate treatment under earlier NEM arrangements from export compensation based on Avoided Cost Calculator values under its Net Billing Tariff. The cited comparison covers PG&E, SCE and SDG&E territories. Other utilities have separately approved arrangements; do not apply this example automatically to another utility or jurisdiction.

Record the actual tariff’s netting interval, import prices, export values, carryover, settlement and charges. A headline such as “one-for-one credit” does not establish that all invoice items are offset or that surplus is paid at the retail purchase rate.

Keep programme rules separate from a calculator’s assumptions. A default entry is not evidence that the customer’s utility offers that treatment.

Separate three electricity flows

Model solar production, electricity consumed directly on site and surplus exported. Also retain imported electricity after solar. Match production and consumption at a resolution appropriate to the tariff; annual totals cannot show whether generation occurs when the customer uses power.

For a simple system without storage, export limitations or other complications, generation divides into onsite consumption and exports. Storage introduces charging, discharge losses and dispatch choices. Do not assign a household a self-consumption percentage solely because its occupants work from home.

A transparent monthly example

Assume hypothetical values, not a tariff quotation or customer result:

Avoided variable purchase cost is 240 × 0.20 = 48 monetary units. Export value before any applicable credit limits or settlement conditions is 360 × 0.05 = 18. The combined screening value is 66, before changes to other charges, taxes or operating costs.

The 360 exported kWh must not also be counted as direct onsite consumption. Nor does a 600 kWh generation total establish a 120-unit bill reduction by multiplying every kWh by the purchase price. Apply the actual credit mechanism and tariff to the customer’s flow schedule.

Reconcile the example against two bills

Add hypothetical customer consumption of 800 kWh and an unchanged fixed monthly charge of 10 monetary units. Assume the export credit offsets variable import charges in that month, with no taxes, minimum bill, demand charge or other adjustment.

• Without solar: 800 × 0.20 + 10 = 170.
• With solar: grid imports are 800 − 240 = 560 kWh. The bill is 560 × 0.20 − 360 × 0.05 + 10 = 104.
• Modeled bill reduction: 170 − 104 = 66, matching the screening value above.

This agreement is an assumption of the example, not a rule about every utility. If credits cannot offset those charges, or settle later, the actual invoice and available credit balance need separate calculation. Do not subtract the 18-unit export credit again from the 104-unit bill: it is already included.

Test sensitivity without changing the energy flows

Keep generation, onsite use and customer consumption fixed. At a hypothetical zero export value, the reduction is 48, from avoided purchases alone. At 0.10 monetary units per exported kWh, it is 84, assuming those credits remain usable against the same charges. These values test an assumption; they do not describe available tariffs or establish which export price the customer will receive.

Compare bills, not only generation revenue

For a stronger estimate, calculate the bill without solar and the bill with solar using the same consumption, period and tariff assumptions. Their difference identifies modeled bill savings. Keep fixed charges, demand charges, minimum bills, taxes and non-offsettable items where they apply.

In an energy-credit arrangement, do not substitute the simplified export-price example for the required netting and settlement rules. Explain how the model implements the actual agreement. Compare its output with a real invoice once the project is operating, using the relevant data and period.

Annual totals are insufficient for a time-dependent tariff

Two customers can consume the same annual amount while using electricity at different times. Likewise, equal annual generation can have different export profiles. Where the tariff varies by time, match load, solar and prices to the relevant intervals, then apply the actual billing rules. An annual average price or a generic “peak export” share can conceal the mismatch.

Check the data timestamps, time zone and daylight-saving handling before joining schedules. Identify gaps and estimation methods. If only monthly bills are available, label the load profile as estimated and test plausible alternatives rather than presenting the assumed timing as measured consumption.

Use the existing calculator as a scenario tool

Open the net-metering savings calculator, inspect the fields and document any assumption that it cannot represent. Use a separate schedule or model when the contract requires more detail. This article does not certify the tool’s current tariff coverage, legal eligibility checks or calculation accuracy; tool QA is recorded separately.

Retain the production source, load basis, entered rates, currency, dates and result. An estimate without those inputs cannot be reproduced. If the calculator uses an annual self-consumption percentage, explain its derivation and the limitations of that simplification.

Batteries and project returns

Compare the same solar project with and without storage. Add installed battery cost, operating limits, losses, degradation and replacement assumptions. Model the actual dispatch rather than selecting a higher self-consumption percentage to manufacture an attractive outcome.

Bill savings alone do not determine payback or NPV. Include project costs, ongoing expenses, financing and confirmed support at their applicable dates. Do not assume a universal tax-credit percentage or promise savings after the initial recovery date are pure profit.

Before accepting a financial estimate

Ask the provider to show the agreement, production and load schedules, bill comparison, exclusions and sensitivity cases. Request a base case without unconfirmed incentives and identify remaining utility approvals. Resolve differences between the advertised calculation and the customer’s tariff before using the result in a sales proposal.

For jurisdiction-specific source navigation, use the state and country guide. For a professional tariff record and connection checks, use the installer reference.

For a software evaluation, inspect the inputs and available reports in SurgePV’s financial workflow with a representative project. Software does not grant interconnection approval or establish current tariff eligibility.

Reviewed September 30, 2026 using the linked DOE and CPUC guidance. The page is an input and calculation guide, distinct from the interactive tool and local policy directory. Arithmetic is illustrative; no retained customer cases, nationwide policy survey or guaranteed benefit is claimed.