Calculator Inputs
Quick Guidance
- Enter realistic costs from bids and takeoffs.
- Subtract rebates that reduce the purchase price.
- For commercial, set kW and start date carefully.
- Use "Custom credit rate" if your case is confirmed.
Example Data Table
| Scenario | Total cost | Eligible | Rate | Credit |
|---|---|---|---|---|
| Residential rooftop | $22,500 | $21,000 | 30% | $6,300 |
| Commercial 800kW | $1,150,000 | $1,100,000 | 30% | $330,000 |
| Commercial w/ bonuses | $2,400,000 | $2,350,000 | 50% | $1,175,000 |
Formula Used
Eligible basis = Included costs − Rebates/SubsidiesCredit value = Eligible basis × (Credit rate ÷ 100)Effective cost = Total cost − Credit valueHow to Use This Calculator
- Choose a credit type (residential or commercial) that matches your project.
- Enter the placed-in-service year and your full cost breakdown.
- Use the toggles to decide which costs are in the eligible basis.
- Add rebates/subsidies that reduce the purchase price of equipment.
- For commercial: enter system size, start date, and any bonuses.
- Click Calculate to see totals, credit value, and payback.
- Use Download CSV or Download PDF to archive the result.
Credit-Eligible Cost Structure
Solar incentives start with the eligible basis, not the invoice total. This calculator lets you include or exclude labor, design, permitting, interconnection, storage, and other costs to match your documentation. Rebates and point-of-sale subsidies can reduce basis, so capture them explicitly to avoid overstating the credit.
Residential Timing and Rate Planning
For homes, the placed-in-service year drives the default credit rate. If you are comparing schedules, run scenarios for the current year and the planned commissioning year, then review the credit value difference. If business use exceeds 20%, the estimator applies a proportional allocation to reflect mixed-use conditions.
Commercial Base Rate and Compliance Drivers
Commercial projects typically begin with a base rate that depends on system size, construction start date, and prevailing wage and apprenticeship compliance. Enter kW AC carefully; systems under 1,000 kW may qualify for a higher base assumption in many planning models. If you are unsure about compliance status, compare 6% and 30% outcomes to understand financial exposure.
Bonus Adders and Allocation Options
Domestic content and energy community selections add percentage points when criteria are satisfied. Low-income adders are shown as selectable uplifts, but real eligibility requires allocation awards and program rules. Use the custom rate field when a finalized rate is known, such as when a tax advisor confirms a blended rate after incentives and allocations.
Interpreting Results for Bids and Owners
The output shows total cost, eligible basis, credit rate, credit value, and an effective cost proxy. If you enter annual savings, the tool provides simple payback before and after the credit to support owner presentations. For bidding, export the CSV for your estimate file and export the PDF for submittals and internal approvals. Many owners also want a what-if view. Change only one variable at a time—rebates, storage inclusion, or bonus eligibility—to isolate the driver. Keep copies of invoices, commissioning records, and compliance certifications, because these typically support the basis and the claimed percentage in a review for your project file.
FAQs
What costs should I include in the eligible basis?
Include the cost lines you can support with contracts, invoices, and commissioning records. Many projects include equipment, installation labor, design, permitting, and interconnection. Use the toggles to model your documentation approach and subtract rebates that reduce purchase price.
Why does the calculator subtract rebates and subsidies?
Some rebates act like purchase-price adjustments and reduce the amount used to calculate the credit. If your incentive is treated differently in your jurisdiction or agreement, set rebates to zero and use a confirmed custom rate based on professional guidance.
How do I use the commercial compliance fields?
Enter kW AC, the construction start date, and whether prevailing wage and apprenticeship requirements are met. These inputs affect the modeled base rate and whether bonus points are treated as 10-point or 2-point adders in this estimator.
What if I already know the exact credit percentage?
Type your percentage into Custom credit rate and leave bonuses as-is. The calculator will use your rate instead of its built-in assumptions. This is the best option when a tax advisor has confirmed a blended rate for your project.
Is the payback calculation a full financial model?
No. Simple payback is a quick ratio: cost divided by annual savings. It does not include financing, escalation, maintenance, performance degradation, or tax appetite limits. Use it for early screening, then validate with a detailed pro forma.
Can I use the exports for bid packages?
Yes. Download CSV to attach to your estimate workbook and download PDF for proposal exhibits. Keep the exported file with the same assumptions you used for pricing, so later revisions can be compared transparently.