The certificate your solar roof prints, and what it sells for

I.How a Philadelphia roof mints a certificate

If you have panels on a South Philadelphia rowhouse or a Northeast warehouse, your system is doing two jobs at once. It pushes kilowatt-hours through your meter and knocks down your PECO bill. It also, quietly, prints a second product you may never see: a certificate that records the clean electricity you made, which someone else is required by state law to buy.

That certificate is a solar renewable energy credit (an SREC, one tradable credit for every megawatt-hour, which is 1,000 kilowatt-hours, that a registry certifies your system produced). It is separate from the power. You consume the electricity yourself; you sell the credit into a market built by Pennsylvania's Alternative Energy Portfolio Standard, the 2004 law (often shortened to AEPS) that tells electricity suppliers how much clean generation they must cover each year, including a dedicated solar slice called the solar carve-out.

II.Where the credit is metered and certified

The credits do not appear on their own. Your installer, or you, registers the system in PJM-GATS (the Generation Attribute Tracking System run by PJM Environmental Information Services, the arm of our regional grid operator that tracks where clean power comes from). Once the system is certified in that registry, its metered output is reported and GATS issues one SREC for each megawatt-hour, stamping it with the year and the fact that it was made in Pennsylvania.

That stamp matters because credits only start counting from the certification date, not from the day you flip the system on. This desk has seen homeowners assume the first sunny month already earned them money, when the registration was still pending. Register early, and keep the meter numbers, because the SREC is the paper trail, not the sunshine.

III.Why a 2017 law changed your payback

For years, the border was open: systems in other states could sell SRECs into Pennsylvania's market, which flooded supply and pinned in-state prices near the floor, at last public report sometimes only a few dollars a credit. A rooftop in Philadelphia was competing against panels hundreds of miles away that had nothing to do with our grid.

Act 40 of 2017 closed that border, so only Pennsylvania-sited systems earn credits that count toward the state's solar carve-out. Supply tightened, and in-state SREC prices lifted off the floor to somewhere on the order of tens of dollars each at last public report. That single change moved the payback math on a city rooftop, though how far depends on where prices sit the week you sell.

IV.The honest math on a rowhouse

Run rough numbers. A typical rowhouse array runs on the order of 5 to 8 kilowatts and might generate roughly 6 to 9 megawatt-hours a year in our climate, cloudy winters and humid summers included, so it earns about 6 to 9 SRECs annually. At a price on the order of tens of dollars each, that is maybe a couple hundred dollars a year on top of the bill savings, and it is the least predictable line in your whole payback.

Treat that income as a bonus, not a plan. SREC prices float, and they are effectively capped by the state's solar alternative compliance payment (the penalty a supplier pays instead of buying a credit, which sets a ceiling on what a credit is worth). If you are weighing an installer's quote, ask whether their payback assumes a fixed SREC price, and discount any number that looks too confident about a market this thin.

V.Worth watching this month

1. Watch for the Pennsylvania PUC's AEPS annual report, usually posted around spring at last public report, which shows the solar share each supplier actually met and roughly where compliance stands.

2. Watch the AEPS reporting-year rollover, which runs on a June 1 cycle, since the required solar percentage steps up over time and tighter targets tend to support credit prices.

3. Watch any PECO default-service or rate filing at the PUC, because the value of the bill you avoid sits right alongside your SREC income and both can move at once.

4. Watch your own GATS certification status if you just energized a system, since credits do not mint until the registry certifies you, and that lag is routine but easy to forget.

Sources on the bench

Pennsylvania PUC, Alternative Energy Portfolio Standard (state regulator, .gov) The agency that administers AEPS; posts the annual compliance reports and the solar alternative compliance payment that caps credit value. · www.puc.pa.gov
PJM-EIS Generation Attribute Tracking System, GATS (regional grid operator registry) Where a Pennsylvania system registers and where each SREC is issued and tracked, one per megawatt-hour certified. · www.pjm-eis.com
Pennsylvania DEP, Alternative Energy Portfolio Standard overview (state agency, .gov) State background on the AEPS program, the solar carve-out, and how qualifying generation is defined. · www.dep.pa.gov
PECO, Solar and Net Metering Your utility's pages on interconnection and net metering, the bill-side savings that sit alongside SREC income. · www.peco.com
Pennsylvania General Assembly, Act 213 of 2004 and Act 40 of 2017 The statute that created AEPS and the 2017 amendment that closed the border so only in-state systems earn qualifying credits. · www.legis.state.pa.us