Enter project assumptions
The page stays in a single vertical flow, while the calculator fields use three columns on large screens, two on medium screens, and one on mobile.
Example data table
This sample scenario shows how yearly savings and cumulative cash flow can develop for a construction-focused solar installation.
| Year | Production (kWh) | Gross Savings | O&M | Net Cash Flow | Cumulative |
|---|---|---|---|---|---|
| 1 | 13,750 | $2,007.50 | $210.00 | $1,797.50 | -$13,865.00 |
| 2 | 13,681 | $2,077.36 | $214.20 | $1,863.16 | -$12,001.84 |
| 3 | 13,613 | $2,149.65 | $218.48 | $1,931.17 | -$10,070.67 |
| 4 | 13,545 | $2,224.46 | $222.85 | $2,001.61 | -$8,069.06 |
| 5 | 13,477 | $2,301.87 | $227.31 | $2,074.56 | -$5,994.50 |
Formula used
Gross Cost = (System Size in kW × 1,000 × Installed Cost per Watt) + Soft Costs
Net Upfront Cost = Gross Cost − Rebate − Tax Credit Value
Tax Credit Value = (Gross Cost − Rebate) × Tax Credit %
Production in Year n = Year 1 Production × (1 − Degradation Rate)n−1
Effective Rate = (Self-Consumption % × Import Rate) + (Export % × Export Rate)
Net Cash Flow = Gross Energy Savings − O&M Cost − Replacement Cost
Break-even occurs when cumulative cash flow becomes zero or positive. Discounted break-even uses present-valued annual cash flows instead.
How to use this calculator
- Enter the proposed solar system size, unit installation cost, and any soft costs.
- Add rebates and tax credits to reduce the starting project cost realistically.
- Estimate first-year production from design software, installer proposals, or site history.
- Split output between self-consumed energy and exported energy using your operating profile.
- Use realistic import, export, inflation, degradation, and maintenance assumptions.
- Add any expected inverter replacement event and define the analysis period.
- Press the calculate button to show results above the form and below the header.
- Review payback, NPV, ROI, yearly cash flow, and export the table as CSV or PDF.
Frequently asked questions
1. What does solar break-even mean?
Solar break-even is the point where cumulative project savings recover the net upfront investment. After that point, the system is producing net financial benefit, assuming your operating and tariff assumptions stay reasonably close to reality.
2. Why are import and export rates entered separately?
Many projects offset on-site energy at a higher retail rate while exported energy earns a lower credit. Separating the two rates gives a more realistic value per kilowatt-hour than assuming every solar unit has identical worth.
3. Why include panel degradation?
Solar modules slowly lose output over time. Including degradation reduces future production slightly each year, which improves long-range accuracy for payback, lifetime savings, and levelized energy cost estimates.
4. Why does the calculator show discounted payback?
Discounted payback recognizes that future money is worth less than money today. It is useful when comparing solar with other construction investments that also use discount rates, capital budgeting rules, or financing benchmarks.
5. What happens if break-even is not reached?
If cumulative cash flow stays negative through the selected analysis period, the calculator reports that break-even is not reached. That usually signals low savings, high project cost, weak export credits, or an overly short review period.
6. Can this be used for commercial construction planning?
Yes. It is well suited for early-stage commercial or institutional planning, especially when you want fast scenario comparisons. Final decisions should still use project-specific engineering, incentives, tariff review, and procurement pricing.
7. How accurate are the savings results?
Results are only as accurate as the assumptions entered. Use realistic production forecasts, utility tariffs, maintenance budgets, and incentive rules. Good assumptions make the calculator useful for screening, budgeting, and investment conversations.
8. Why does the calculator include LCOE and IRR?
LCOE helps compare solar energy cost against utility supply or competing systems. IRR shows the project’s implied annual return. Together, they add decision-making context beyond simple payback alone.