Calculator Inputs
Enter technical, financial, tax, and financing assumptions. The form stays in one stacked page layout, while input cards adapt to screen size.
Example Data Table
These sample scenarios illustrate how project size, incentives, and financing can change payback and return outcomes for commercial systems.
| Scenario | System Size | Installed Cost/W | Utility Rate | Upfront Incentives | Debt Share | Estimated Payback | Estimated ROI |
|---|---|---|---|---|---|---|---|
| Warehouse Roof | 180 kW | $1.34 | $0.11/kWh | $12,000 | 35% | 7.9 years | 143% |
| Office Complex | 250 kW | $1.25 | $0.12/kWh | $20,000 | 40% | 6.8 years | 171% |
| Cold Storage Site | 400 kW | $1.18 | $0.15/kWh | $28,000 | 50% | 5.7 years | 224% |
Formula Used
This calculator combines project cost, energy savings, tax benefits, financing, and discounted cash flow analysis to estimate commercial solar returns.
- Gross Project Cost = System Size (kW) × 1,000 × Installed Cost per Watt
- Eligible Cost = Gross Project Cost − Upfront Incentives and Rebates
- ITC Amount = Eligible Cost × Tax Credit Rate
- Depreciable Basis = Eligible Cost − 50% of ITC Amount
- Bonus Depreciation = Depreciable Basis × Bonus Depreciation Rate
- Remaining MACRS Basis = Depreciable Basis − Bonus Depreciation
- Yearly Production = Year 1 Production × (1 − Degradation Rate)Year−1
- Energy Savings = Yearly Production × Escalated Utility Rate
- Escalated Utility Rate = Starting Utility Rate × (1 + Escalation Rate)Year−1
- Escalated O&M = Year 1 O&M × (1 + O&M Escalation)Year−1
- Depreciation Tax Shield = Depreciation Expense × Corporate Tax Rate
- Net Cash Flow = Energy Savings − O&M − Debt Service + Tax Shield + ITC Benefit
- NPV = Sum of discounted cash flows including initial equity outlay
- ROI = (Total Net Profit ÷ Initial Equity Investment) × 100
- IRR = Discount rate where total project NPV equals zero
How to Use This Calculator
- Enter the commercial system size and installed cost assumptions.
- Add expected production, degradation, and current utility tariff values.
- Include O&M costs, escalation rates, and any available incentives.
- Set tax credit, tax rate, and bonus depreciation assumptions.
- Add debt share, loan rate, and loan term if financing applies.
- Choose the analysis period and discount rate for valuation.
- Click the calculation button to view ROI, payback, NPV, IRR, and yearly cash flows.
- Use the CSV and PDF buttons to export the modeled output for internal review, budgeting, or presentation.
Frequently Asked Questions
1) What does this calculator measure?
It estimates commercial solar project returns using energy savings, tax credit value, depreciation tax shield, maintenance costs, financing payments, and discounted cash flow metrics.
2) Is ROI the same as IRR?
No. ROI shows total gain versus equity invested. IRR shows the annualized rate where discounted project cash flows equal zero.
3) Why does the calculator include degradation?
Solar modules gradually produce less electricity over time. Degradation reduces future output and lowers long-term savings if rates stay unchanged.
4) Why are utility escalation and O&M escalation separate?
Electricity prices and operating costs often rise at different speeds. Modeling both separately gives more realistic long-term project economics.
5) How is the tax credit handled?
The calculator applies the tax credit to eligible cost after rebates. It then adds that benefit in year one for cash flow analysis.
6) What depreciation approach is used?
It uses bonus depreciation plus a five-year MACRS-style schedule on the remaining basis to estimate annual tax shield value.
7) Does financing improve ROI?
It can. Debt lowers upfront equity but adds fixed annual payments. Whether ROI improves depends on savings strength, tax benefits, and borrowing cost.
8) Should I rely on this alone for investment approval?
Use it as a planning tool. Final decisions should also consider engineering design, interconnection timing, insurance, tax advice, and site-specific risk.