Plan system size, price, and financing options fast. Model production, degradation, and rate escalation easily. Download detailed yearly cashflows as CSV or PDF files.
Use this example to verify inputs and understand outputs.
| Scenario | System | Cost/W | Rate | Year‑1 kWh/kW | Breakeven | End net gain |
|---|---|---|---|---|---|---|
| Sample home | 5.0 kW | 0.90 | 0.16/kWh | 1450 | ~6–9 years | Positive after 25 years |
| Higher rates | 5.0 kW | 0.90 | 0.22/kWh | 1450 | ~4–7 years | Higher lifetime gain |
| More shading | 5.0 kW | 0.90 | 0.16/kWh | 1450 | Later | Lower lifetime gain |
The calculator’s exact numbers depend on all cost and rate assumptions.
Breakeven starts with your net system cost: size in kilowatts, installed cost per watt, and fixed project items. Incentives reduce that base cost, so entering a 10% rebate or a flat grant can shift payback by years. Use realistic quotes, include permits, wiring upgrades, and warranty add-ons. When financing is selected, the down payment becomes the year‑0 outflow and the remaining balance turns into payments that reduce annual cashflow.
Year‑1 production is modeled as kWh per kW, then adjusted for shading and losses. A common range is 1,200–1,700 kWh per kW, depending on climate and tilt. Degradation reduces output over time; 0.3%–0.8% per year is often used for modern panels. If your roof has partial shade, increasing losses from 5% to 15% will lower savings every year and delay breakeven.
Savings depend on how each kWh is valued. The calculator applies a blended rate: self‑consumed energy offsets retail pricing, while exported energy is credited at a percentage of that rate. If export credit is 80% and self‑consumption is 70%, most value comes from on‑site use. Rate escalation models rising tariffs; a 4% annual increase compounds over decades and can materially improve lifetime savings versus a flat rate.
Annual operating costs reduce net benefit, so include cleaning, monitoring fees, and minor repairs in O&M. Insurance is optional but relevant for some lenders or homeowners. The inverter replacement line captures a one‑time midlife expense, often around year 10–15. Loan payments are allocated by year from a monthly amortization schedule, so early years may show slower cumulative recovery even when gross savings are strong.
Breakeven is reached when cumulative cashflow turns non‑negative, with fractional years estimated from the crossing point. NPV discounts future cashflows using your discount rate, reflecting opportunity cost and risk. IRR is the discount rate that makes NPV equal zero, useful for comparing projects. LCOE divides discounted costs by discounted energy to estimate an effective cost per kWh for the modeled system.
Breakeven is the first year when total cumulative cashflow becomes zero or positive, after accounting for net cost, savings, operating costs, replacements, and optional loan payments.
Start with an installer estimate or a local solar production benchmark, then adjust for tilt, orientation, and shading. Conservative inputs help avoid overly optimistic payback expectations.
On‑site use offsets the full retail rate, while exported energy may earn less. Lower export credit makes storage or load shifting more valuable, and it can extend breakeven.
Many users choose 5%–10% to reflect borrowing costs or alternative investments. A higher rate reduces NPV and can make long‑term savings appear less valuable.
This version models solar generation only. You can approximate storage by increasing self‑consumption and adding battery costs to fixed costs or annual costs, but results will be simplified.
IRR requires cashflows that cross from negative to positive in a way that yields a unique solution. If the cashflow pattern never changes sign, IRR may not exist.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.