Federal + State + Utility Rebate Stacking Rules (2026)
Federal credits, state credits, and utility rebates generally stack — but the order of operations matters and a few combinations cancel each other. The key rule: state and utility rebates typically reduce the federal credit basis (net cost), while federal credits do NOT reduce state credit basis. So apply rebates first, then calculate state credits on full cost, then calculate federal credits on net cost. SRECs and performance-based incentives are revenue, not cost offsets — they do not reduce basis. The biggest "do not stack" rules: 25C and HEEHRA cannot apply to the same item (pick the higher), and 30D and commercial 45W cannot apply to the same vehicle.
The Order of Operations
Step 1: Subtract utility rebates from total cost. Step 2: Subtract state rebates from remaining cost. Step 3: Calculate state tax credits on full pre-rebate cost (most states). Step 4: Calculate federal tax credits on the net cost (post-rebate). Step 5: Apply credits against tax owed in their respective filings.
Solar Stack Example: California
$25,000 8 kW solar + 13.5 kWh battery in San Francisco. SGIP General Market battery rebate = $2,025 → net basis $22,975. Federal 25D 30% = $6,892. State property tax exemption (no $ value, but ~$300/yr saved). Net cost $16,083 effectively, or 36% incentive coverage.
Heat Pump Stack Example: New York
$14,000 3-ton ducted ASHP in Buffalo. NYSERDA Clean Heat $4,500 → net basis $9,500. Federal 25C 30% = $2,000 cap. Total incentives $6,500 on $14,000. Income-qualified households add HEEHRA up to $8,000.
EV Stack Example: New Jersey
$42,000 new EV. Federal 30D $7,500 POS + Charge Up NJ $4,000 POS + sales-tax exemption ~$2,800 = $14,300 stacked. Effective price $27,700. State credits do not reduce 30D — vehicle qualifies on its own merits.
What Does NOT Stack
25C and HEEHRA on same item — pick the higher (HEEHRA wins for income-qualified, 25C wins for higher-income). 30D and 45W on same vehicle — buy or lease, not both. Federal 25D and commercial Section 48 ITC — residential or commercial, not both.
What Does Not Reduce Basis
SREC payments (revenue, not cost offset). Performance-based incentives that flow over time. Net metering credits (utility billing, not incentive). Time-of-use rate savings. HOA assessments unrelated to install.