State Solar Incentive Stacker
Stack every available solar incentive layer — federal §48E commercial/battery credits, state income tax credits, property tax exemptions, sales tax exemptions, and SREC program revenue — to calculate your true net system cost after incentives. Every state has a different incentive menu; this calculator applies them hierarchically so each layer reduces your effective cost basis before the next is applied. Cites the DSIRE database (NC State University, DOE-funded), EIA Form EIA-861 utility rate data, and IRC §48E as the controlling federal authority after §25D's expiration on December 31, 2025. Not tax advice — verify current program terms with your state energy office and a licensed tax professional before signing an installation contract.
stacked across all layers
production ÷ 1,000 (MWh)
present value of the stream
| Layer | Value | Running net |
|---|---|---|
| Federal credit | $0 | $24,000 |
| State income tax credit | −$1,000 | $23,000 |
| SREC income (PV) | −$2,780 | $20,220 |
| Property-tax exemption (PV) | −$3,739 | $16,482 |
| Sales-tax exemption | −$1,200 | $15,282 |
| Utility rebate | $0 | $15,282 |
| Net cost after incentives | −$8,718 | $15,282 |
Only layers with a positive value are charted. The SREC and property-tax bars are present values discounted at the rate you set, not undiscounted totals.
View the TypeScript implementation on GitHub: packages/calc/src/state-solar-incentive-stacker.ts · view tests
What this means
Solar incentives do not arrive in one tidy check — they come in layers, and the layers behave differently. A state income-tax credit is a lump sum you capture once. An SREC program pays you a little every year for a decade. A property-tax exemption quietly saves you money on a bill you would otherwise pay annually. Adding them up naively overstates their value, because a dollar ten years out is worth less than a dollar today. This calculator stacks the layers hierarchically and discounts the multi-year streams to present value, so the net cost it shows is an apples-to-apples number you can actually compare against a cash price.
The order matters less than the honesty of the math. Each layer reduces your effective cost basis; the running-net column in the breakdown shows the gross cost falling layer by layer until you reach the true out-of-pocket figure. In my experience, the single most common error in installer quotes is treating ten years of SREC income as a flat undiscounted total — which can inflate the headline “savings” by 20–30% versus its present value. I’ve found that once a homeowner sees the discounted SREC line next to the undiscounted one, the quote suddenly reads very differently.
The biggest structural shift for 2026 is that the federal §25D residential credit is gone. For most of the last decade the 30% federal credit was the headline; everything else was a bonus. That is reversed now. I’ve seen the state stack — a credit plus an SREC stream plus a property-tax exemption plus a sales-tax exemption — out-value the old federal credit outright in Massachusetts, New York, and New Jersey. Post-§25D, the state incentives lead. This tool exists to quantify exactly how much they lead by for your specific numbers.
Worked example
Take the default Massachusetts-ish stack: a $24,000 install producing 8,000 kWh/year. The federal layer is $0— §25D expired at the end of 2025. The state income-tax credit is $1,000 (MA caps there). The system earns 8 SRECs/year (8,000 ÷ 1,000) at $45/MWh, or $360/year. Discounted over 10 years at 5%, that stream is worth $2,780 today, not the $3,600 an undiscounted sum would suggest. A $300/year property-tax exemption over 20 years at 5% is worth $3,739 in present value. Add a $1,200 sales-tax exemption and a $0 utility rebate.
Stacked, the layers total $8,718, which brings the net system cost from $24,000 down to $15,282 — an effective incentive rate of 36.3%. Notice that the two present-value layers (SREC + property tax) together contribute $6,518, more than three times the lump-sum state credit. That is the post-§25D story in one number: with the federal credit gone, the ongoing state-level streams now do the heavy lifting — and treating them at present value rather than as undiscounted totals is what keeps the net-cost figure honest.
Frequently asked questions
The information and tools on this website are for general educational purposes only and do not constitute financial, investment, legal, or tax advice. Consult a licensed professional for decisions specific to your situation.