Your Solar Credits Peak in July and Expire in Spring. What to Check Before They Do
Export credits banked over summer are drawn down in winter and often cashed out at a fraction of their value, and the rules that decide how much differ by state and by utility.
Nikolai Dragomir4 min
The call usually comes in November or February, and it sounds like a hardware failure. The array performed all summer, the bill sat near zero for months, and then a three figure balance arrived with no warning and no obvious cause. Nine times out of ten the panels are fine, the inverter is reporting normally, and what changed is the arithmetic the utility applies to the electricity you sent back. Export compensation is seasonal by design, and the season you are in decides whether a kilowatt hour leaving your meter is worth retail, wholesale, or something in between.
The winter bill is usually a netting interval, not a fault
Before anyone climbs on the roof, look at how your credits are counted. Some states net your production against your consumption over a full year, so a summer surplus quietly carries into January. Others net monthly, which means October's surplus is settled in October and cannot rescue December. A growing number net on an hourly or even instantaneous basis, so power exported at noon is priced separately from power imported at seven in the evening, and a house with no battery buys back most of what it sold. That single design choice explains more winter bills than every equipment problem combined.
Find the true-up date before it finds you
If your utility runs annual netting, one date on the calendar governs the whole account, and most homeowners could not name theirs. On that anniversary, banked credits are settled: sometimes they roll forward, sometimes they are paid out at an avoided cost rate that is a small fraction of the retail rate you were crediting them at all year, and sometimes they simply expire. A system sized to finish the year at zero behaves very differently from one that finishes with a large unused balance. The date is printed on your bill, usually in small type near the account summary, and the utility's solar billing line will confirm it in one call.
Knowing the date changes what you do with the shoulder months. If your true-up lands in the spring, the credits you are burning now are the ones you earned in July, and running the dryer at midday in March costs you nothing you were going to keep. If it lands in the fall, the same behavior in March is spending money.
Seasonal rate windows move, and the export price moves with them
Where compensation is tied to time of use, the definition of peak is itself seasonal. Summer schedules often place peak in the late afternoon and evening, when a south facing array is already fading. Winter schedules frequently add a morning peak, before the sun clears the trees, and shift the evening block earlier. Under net billing structures, the export rate is published as a schedule of hourly values that changes month to month, so the same exported kilowatt hour is worth several times more in an August evening than in a mild April afternoon. The Federal Energy Regulatory Commission is responsible for the federal framework governing purchases from small generators, but the seasonal rate design that actually shows up on your bill is set by your state commission and your utility.
What your tariff protects, and how long
The interconnection agreement you signed is a contract, and in most states it carries a legacy period: a defined number of years during which the compensation rules in force at the date of approval continue to apply to your system, even after the state adopts something less generous for new customers. Those periods vary widely, and they are usually tied to the date the utility granted permission to operate rather than the date you signed with the installer. Adding panels, replacing an inverter with a larger one, or moving the system can, under some tariffs, end the legacy period and move the account onto current rules. Ask before you expand, not after.
Consumer protections vary by state as well. Several require solar sellers to give written disclosure of the compensation structure and its expiration in plain language before signing, and most state commissions publish the applicable tariff sheets and run a complaint process for billing disputes.
What to handle this week and what can wait
This week: locate your true-up date, the name of your rate schedule, and the legacy period end date, and keep all three in one place. Call the utility's solar billing group rather than the installer, because the installer cannot see the tariff applied to your account. What can wait until spring is everything structural: battery sizing, panel additions, load shifting habits. Those decisions are better made with a full year of interval data in hand, and a February decision made from one alarming bill tends to buy capacity the house does not need.
The number that matters is not what the array produced. It is what the meter's exports were credited at, hour by hour, under a schedule your state wrote and your utility administers, and that document is available to you for the asking.