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The cost of solar

Sticker price was $55,972. After the New York State credit and the federal ITC, it came down to $31,382. Credits covered $24,590 of it.

I financed that over 15 years at 6% APR — $31,382.10, or about $265 a month. I paid the $5,000 state credit up front instead of borrowing it. No sense paying interest on money I'm getting back at tax time.

From month one I'm paying $265 for the loan and $41 in fixed charges. That's $306 a month. Right now the same electricity costs me $356. So I'm about $51 a month less — on a bill that keeps going up.

Both columns include the fixed charges and the tax on them. The Customer Benefit Contribution is what New York adds when you connect solar: going solar raises my standing charge by $20.88 a month.

Over the full term I'll repay $47,668 on $31,382.10 borrowed. That's $16,286 in interest. Borrowing isn't free.

What if prices never go up again?

So let's assume the worst. Today's rate, frozen for the whole 25-year life of the array. No more increases, ever — while the panels age at the rate their warranty allows for. This isn't a forecast: it's the floor. It answers one question, which is what this thing is worth if I'm completely wrong about prices going up.

Years 1–15, while I'm paying the loan: $51 a month, $8,031 total. Years 16–25, after it's paid off, the payment goes away and only the fixed charges are left: $315 a month, $35,845.

$43,876 over 25 years — and that's the pessimistic case. The interest is already in that number. The loan payment is principal plus interest, so it comes out once. Subtracting it again would be counting it twice.

One row per year, at today's rate. The array is sized at about a year's usage, so generation starts level with what I use and slips below as the panels age — the warranty guarantees 98% of rated output in year one and 92% at year 25. What gets avoided is what the panels make, valued at today's rate, which is why both kilowatt-hour columns are here.

The extra charge is the Customer Benefit Contribution — the only fixed charge solar adds. The customer charge itself is missing on purpose: I pay it identically either way, so it cancels.

My rate went up 42% in two years, so a flat rate isn't a world I expect. Whatever actually happens to prices, the number should come out better than this one.

Why I didn't go bigger

16.56 kW lands right around 100% of what I use in a year. That's on purpose. New York nets my generation against my usage every month at full retail value. But whatever surplus is still sitting there at the annual true-up gets cashed out at a much lower avoided-cost rate.

So a bigger array wouldn't earn me more on that surplus. It would just move more of my generation into the bucket that pays less.

Sized this way, nearly every kilowatt-hour the roof makes cancels one I'd otherwise buy at 23.9¢. Build bigger and the extra doesn't cancel anything — it gets sold back at a fraction of that. A kilowatt-hour I don't have to buy is worth more to me than one I sell.