Turn sun hours into annual energy and income. Add tariffs, incentives, and performance losses easily. See output, savings, and payback in seconds now here.
| System (kW) | Sun hours/day | PR (%) | Self-use (%) | Year 1 kWh | Year 1 net benefit |
|---|---|---|---|---|---|
| 6.00 | 5.20 | 82 | 65 | ~9,600 | ~1,520 |
| 10.00 | 4.60 | 80 | 50 | ~13,400 | ~1,880 |
| 3.50 | 5.80 | 84 | 80 | ~6,200 | ~1,020 |
Year 1 energy (kWh): kW × peakSunHours × 365 × (PR/100) × (Availability/100)
Year y energy (kWh): Year1kWh × (1 − Degradation)^ (y − 1)
Onsite and export split: Onsite = kWh × SelfConsumption, Export = kWh − Onsite
Annual savings: Onsite × GridRate
Annual export revenue: Export × ExportRate
Annual net benefit: (Savings + Revenue) − O&M
Simple payback (years): (Upfront − Incentives) ÷ Year1NetBenefit
NPV: −NetCost + Σ(NetBenefit_y ÷ (1+DiscountRate)^y)
LCOE (simplified): DiscountedCosts ÷ DiscountedEnergy
Production starts with system size and peak sun hours, then scales down using performance ratio and availability. A 6 kW array at 5.2 sun hours with 82% PR and 99% availability yields about 9,600 kWh in Year 1. Degradation reduces output each year, so a 0.6% rate trims Year 25 energy to roughly 86% of Year 1.
Value depends on how much energy offsets your own usage versus being exported. If self-consumption is 65%, most kWh are priced at the grid rate, while exports earn the export rate. With onsite energy valued at 0.18 per kWh and exports at 0.08, the same 9,600 kWh can produce different benefits depending on load shape. Annual O&M is subtracted so net benefit reflects upkeep.
Small input shifts can move payback by years. Increasing PR from 80% to 85% raises energy by 6.25%. Raising self-consumption from 50% to 75% reallocates value from export credits to higher-priced onsite savings. If grid rates rise over time, savings usually accelerate; if export rates fall, revenue becomes less important. Use multiple runs to bracket best-case and conservative assumptions rather than relying on a single scenario.
NPV discounts future net benefits to today’s value, letting you compare solar against other uses of cash. A higher discount rate reduces NPV and can delay discounted payback, even if simple payback looks attractive. LCOE divides discounted costs by discounted energy, producing a cost per kWh that can be compared to your effective grid price. When LCOE is below your blended rate, the project is typically economically favorable.
For planning, combine this estimate with site realities: shading, soiling, inverter clipping, and policy constraints. Use production monitoring data when available to refine PR and downtime. Treat incentives as one-time reductions to upfront cost and verify eligibility windows. For commercial sites, align self-consumption with operating hours; storage can increase onsite use but adds cost. Revisit inputs annually to track performance and financial expectations.
Use long‑term solar resource data for your city or nearest weather station. Many solar mapping tools report average daily peak sun hours by month; average them or use an annual value for a quick estimate.
Typical residential systems often fall between 75% and 85%. Use lower values for heavy shading, high temperatures, or older equipment. Use higher values for well‑designed arrays with good ventilation and monitoring.
Onsite energy offsets electricity you would otherwise buy, so it is valued at your retail rate. Exported energy may earn a lower credit or feed‑in tariff set by your utility or policy.
Start with your daytime load profile. Homes without storage may self‑consume 30%–70% depending on occupancy and appliance timing. Businesses operating during daylight can often exceed 70%. Run a few scenarios to bracket results.
If Year 1 net benefit is zero or negative, payback cannot be calculated. This can happen when export rates are very low, O&M is high, or self‑consumption is small. Adjust inputs to reflect your situation.
It estimates avoided emissions by multiplying solar kWh by grid emissions intensity. Enter your region’s kg CO₂ per kWh to display Year 1 avoided tons. Set it to 0 to hide the CO₂ line.
This tool provides estimates based on your inputs and simplified assumptions. Actual solar output and savings vary with weather, shading, equipment, tariffs, and policy rules. For investment decisions, consider a site assessment and professional guidance.
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.