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What it cost, and how it is paid for

The array is $55,972 at sticker. After the New York State credit and the lessor's monetised federal ITC, it is $31,382 — $24,590 of it covered by credits.

That balance is financed over 15 years at 6% APR: $31,382.10 of principal, about $265 a month. The $5,000 state credit is paid up front rather than financed, so it is not sitting on the loan accruing interest while a refund is waited on.

From month one that is $265 of loan plus $41 of fixed charges — $306 a month, against the $356 this house currently pays for the same electricity. About $51 a month less, on a bill that has been climbing.

Both sides count fixed charges, and both are taxed. Today: $336 of electricity plus $20.12 of customer charge. After: $265 of loan, plus that same $20.12, plus $20.88 for the Customer Benefit Contribution New York adds on interconnection. Going solar raises the standing charge, and a comparison that quietly dropped it — or left it untaxed while taxing the other side — would be flattering itself.

Over the full term that is $47,668 repaid on $31,382.10 borrowed — $16,286 of interest. Financing the array is not free, and a payback figure that ignores it is not a payback figure.

If the price of electricity never rises again

Everything above uses today's rate. This does too — and then assumes it never changes again, for the array's whole 25 year life. That is not a forecast. It is the pessimistic case, the floor under the numbers, and it is here to answer what the array is worth if the last three years of price rises simply stop.

Years 1–15, while the loan runs: $51 a month, $9,112 in total. Years 16–25, once it is paid off, the payment disappears and only the fixed charges remain: $315 a month, $37,853.

$46,964 over 25 years, on a flat rate that never moves. The interest above is already inside that figure — the loan payment is principal plus interest, so it is netted out once, where it belongs, rather than twice.

The rate has risen 42% in two years, so a flat rate is an unlikely world and the real figure is probably better than this. That is context for why the floor is conservative, not a projection — nothing on this page forecasts a price.

Why it is not bigger

A 16.56 kW array lands near 100% of a typical year's use, and stopping there is deliberate. New York nets generation against consumption each month at full retail value, but whatever surplus is still banked at the annual true-up is cashed out at a much lower avoided-cost rate.

So oversizing does not buy extra savings on the surplus — it makes the surplus worth less per kilowatt-hour. Sizing to land at or just under annual use means effectively every kilowatt-hour generated offsets one bought at retail, which is the most any of them can be worth.