Net Metering, Net Billing, Buy-All: What Exports Pay

An Arizona homeowner who joined APS's net billing rider in 2017 is still paid 12.9 cents for every kilowatt-hour their roof exports. A neighbour interconnecting the identical array this month is paid 6.171 cents (Rate Rider RCP, A.C.C. No. 6241, Revision No. 10, effective 1 September 2025 under Decision No. 81439, read 22 August 2026). Same panels, same roofline, same grid: the two houses are 52% apart on the strength of the year the interconnection paperwork went in. Arizona replaced net metering with net billing, and the cut arrives through a schedule of annual tranches printed on one page of a rider.

That number — what the utility pays for a kWh you send back — is not on your pre-solar bill, and it is not the retail rate you worked out from it. The four numbers on your own bill price the kWh you stop buying. This is the other half: the kWh you hand over, priced by a separate document that a house without panels never receives.

Three mechanisms, and the one question that separates them

Strip away the branding and the question is: what does the meter measure, and over what interval?

Net metering measures the net. Export flows backwards through the same register, and at the end of the billing period you are billed on the difference. A kWh out cancels a kWh in, so the export is worth exactly the retail rate — delivery and rider components included, because you never bought that kWh at all. New Jersey's rule is a clean specimen: the utility "shall reduce the customer-generator's bill for the next monthly billing period to compensate for the excess electricity from the customer-generator in the previous billing period," carries that credit "from monthly billing period to monthly billing period," and at the end of the annualized period compensates the customer "for any excess kilowatt hours generated, at the electric power supplier's or basic generation service provider's avoided cost of wholesale power" (N.J.A.C. 14:8-4.3(c)–(e), read 22 August 2026).

Net billing measures export as it happens and buys it at a stated price. The RCP rider says so plainly: the company "will meter this Export Energy on an instantaneous basis and provide a monthly bill credit based on the purchase rate in this schedule." There is no banking of kilowatt-hours. A kWh you use at the moment you make it is worth the retail rate you avoided; a kWh that leaves the house is worth 6.171 cents. Those are now two different prices for the same kWh, and that gap is what the bill-savings case for a battery is built out of.

Buy-all/sell-all does not net anything. Austin Energy's Value of Solar is the textbook version: "Austin Energy meters your solar production and credits 100% of that production at the Value of Solar rate," and separately "charges solar customers for all their energy consumption," whether it came from the grid or your own roof (Value of Solar Rate, read 22 August 2026). A residential non-demand account is credited 9.91 cents per kWh, a figure the page marks "effective March 1, 2023 and subject to change." The Value-of-Solar Rider in Austin Energy's electric tariff dated 1 November 2025 shows what sits inside it — 7.61 cents of avoided cost plus 2.30 cents of societal benefit — and commits to no calendar beyond a line saying the rates, methodology and inputs "will be re-assessed and updated during the budget process." Read the current number; do not carry this one forward.

Which one you are on: five places to look

1. The tariff library, not the solar page. Search it for partial requirements, net metering, net billing, export credit, value of solar, solar purchase. APS files its residential solar arrangement under "Partial Requirements Service for New On-Site Solar Distributed Generation." The phrase "net billing" appears nowhere in that title.
2. The unit of the credit. Kilowatt-hours on the bill means net metering. Dollars means somebody applied a purchase rate, and you need to know which one.
3. The metering requirement. RCP requires an AMI meter for the generation and one for service. A tariff demanding a separate production meter is telling you it intends to buy production, not net it.
4. DSIRE, run by the N.C. Clean Energy Technology Center, for the state-level shape. Treat it as an index: it tells you which docket and which program to look for. The tariff sheet still governs, and it changes between updates.
5. The date on the sheet. RCP is Revision 10. The retail schedule underneath it is a different document with a different date. Both matter, and a PDF saved last year is not the same document.

The netting interval decides more than the sell rate

Most comparisons stop at the sell rate. The interval is worth more.

Net an Arizona system monthly, the way New Jersey does, and 4,800 exported kWh get credited at the retail off-peak rate of 15.0479 cents instead of 6.171: $722 a year against the $296 the tariff actually pays. The whole $426 hangs on one word in the rider — instantaneous — and a spreadsheet built on the New Jersey model will never flag it, because every line in that spreadsheet is arithmetically correct.

Instantaneous netting has a second consequence. It turns your load shape into an input. Under monthly netting a kWh made at noon and a kWh used at 9 p.m. cancel each other on paper; under instantaneous netting they never meet, so the noon kWh sells cheap and the 9 p.m. kWh is bought at full price. Getting that split right needs the interval data your own meter already records, not a rule of thumb.

One 8,000 kWh year, three structures, one tariff

Hold everything constant except the mechanism. A house on APS Rate Schedule TOU-E, 5.0 kW-dc on the roof, 8,000 kWh a year, 40% of it consumed the instant it is made.

TOU-E prints bundled energy charges of 34.396 cents on-peak and 12.345 cents off-peak in summer, 32.543 and 12.351 in winter, and 3.495 cents super off-peak, which runs 10 a.m. to 3 p.m. on winter weekdays (Rate Schedule TOU-E, A.C.C. No. 6154, Revision No. 3, effective 8 March 2024, read 22 August 2026). Bundled is not final. Adjustment schedules stack on top, each resetting on its own annual cycle — DSMAC-1 in January, PSA-1 in February, TCA-1 in June, LFCR in November — so the stack is never more than a few months from moving. For a solar house on TOU-E it currently comes to (APS rates, schedules and adjustors, all read 22 August 2026):

PSA-1    historical 0.004520 + forward 0.012457   1.6977 c/kWh   Rev 31, eff 1 Feb 2026
TCA-1    residential 0.005358                     0.5358         Rev 24, eff 1 Jun 2026
DSMAC-1  all residential kWh 0.000754             0.0754         Rev 15, eff 1 Jan 2026
LFCR     energy-only rate 0.00246                 0.2460         Rev 15, eff 1 Dec 2025
CRS-1    court resolution 0.001480                0.1480         Rev  1, eff 8 Mar 2024
TEAM, SRB-1  every component 0.000000             0.0000
                                                 --------
                                                  2.7029 c/kWh

So a kWh you keep is worth 15.0479 cents off-peak in summer, 37.099 on-peak, and 6.1979 cents inside the winter super off-peak window. Sales tax sits on top of all three; treat them as floors.

All three lines are net of the Grid Access Charge, which TOU-E adds to any account with an on-site generation system whatever rider handles the exports: $0.242 per kW-dc a month, $14.52 a year on 5 kW-dc. It falls on all three equally, so it settles no argument between them — it is simply $14.52 that no proposal shows you. The buy-all row carries one condition the others do not: Austin's rider caps each month's credit at that month's electric charges and banks the remainder, so $778 is collectible only if there are electric charges across the year to absorb it.

One item goes the other way, and it is not in the table. A residential customer who interconnected after 1 February 2013 pays a flat $2.09 a month under Adjustment Schedule REAC-1, Revision 21, instead of 0.6214 cents per kWh capped at $2.49. Past roughly 400 kWh in a month the cap is what a non-solar neighbour pays, which puts the flat charge about $4.80 a year in your favour — a reminder that going solar edits several lines you did not expect.

Same roof, same production, same retail tariff. Net billing returns 64% of what net metering returns; buy-all/sell-all returns 65%. No assumption about degradation, escalation, or financing has been made yet, and a third of the annual benefit has already been settled by how the meter is wired.

Notice what the 40% self-consumption assumption did. Under net billing it is the dominant lever. Under the other two it does nothing at all — set it to 10% or 90% and both figures stay exactly where they are. Worth knowing before pricing a battery for bill savings rather than backup.

The winter hour when exporting beats using it

Put the two prices side by side hour by hour and something odd falls out of the Arizona numbers.

In that winter midday window the two agree to within three hundredths of a cent. A battery charging at 11 a.m. in January to discharge at 9 p.m. is doing real work; it moves a 6.2 cent kWh into a 15.05 cent slot. But advice of the form "always self-consume" is, inside that window, worth 0.027 cents per kWh. The rule is not general. It is a comparison between two rates your own tariff prints, and both of them move — the adjustor stack on four separate dates through the year, the export tranche each September for whoever interconnects next.

Ten years, not twenty-five, is what the lock covers

RCP's tranche table is the page to photograph and keep. Each year's new customers get their own rate: 12.9 cents for the 2017 tranche, 10.45 for 2019–20, 8.465 for 2022, 6.857 for 2024, and 6.171 for the tranche running 1 September 2025 to 31 August 2026. The rider sets each one "effective September 1 each year or as determined by the Commission" and adds that the rate "may not be reduced by more than 10% each year." The floor under the next tranche is therefore arithmetic rather than news: 6.171 × 0.9 = 5.5539 cents. That figure is computed off the rider, not published by anyone — the Commission can land above it, or move the date — but a model that holds 6.171 flat is assuming something the tariff never promised.

Three conditions sit around that lock, and each has cost somebody money:

• It runs ten years from interconnection, then the credit becomes whatever tranche is current. A 25-year proposal holding today's export rate flat is asserting 15 years the tariff does not underwrite. Ask for the model rerun with a lower rate from year 11.
• Adding panels later can end it. A "material increase in capacity" — the rider defines it as 10% or 1 kW-ac, whichever is greater — drops you onto the current rate, locked for ten years minus the years already used, and the same clause caps total increases across the whole ten-year term at that figure. Undersizing now and topping up in 2030 is not a free option.
• The rate follows the site, not you. Move the system to another house and the ten-year lock goes. Move into a house already served under the rider and you inherit its tranche.

New Jersey's equivalent is quieter but real: the customer-generator gets one opportunity to choose the month that starts the annualized period, and everything exported above consumption across that year is cashed out at wholesale avoided cost rather than retail. Choose the month badly and you push your surplus into the true-up instead of against your bills.

Find the rider before you find an installer

Open your utility's tariff library today, before there is a proposal to argue with. Find the rider your house will be moved onto the day the system energises — it will not be the schedule you are on now — and write down four things: the sell rate, the netting interval, how long the rate is locked, and what happens to unused credit.

Then take those four to the quote. A proposal that shows annual savings without naming the export mechanism has priced your exported kWh at something, and the twelve items a proposal has to put in writing include the rate it assumed. If it valued exports at retail on a net billing tariff, that is the $426 from earlier — every year, in the direction that shortens payback.