Definition
Specific yield is the annual energy production per unit of installed DC nameplate capacity, expressed in kWh/kWp/year. It captures the combined effect of site irradiance, system efficiency, and orientation in a single normalized number.
Quick Facts
| Field | Detail |
|---|---|
| Term | Specific Yield |
| Category | Solar Engineering / Performance |
| Engineering Discipline | Energy Modeling, Bankability |
| Units | kWh/kWp/year |
| Difficulty Level | Beginner to Intermediate |
Specific Yield Benchmarks (P50, Year 1)
| Region | Specific Yield (kWh/kWp/yr) |
|---|---|
| Saudi Arabia / Atacama | 2,100–2,400 |
| US Southwest (NM, AZ, NV) | 1,800–2,100 |
| Rajasthan India | 1,700–1,900 |
| Spain (south) | 1,600–1,850 |
| Texas / Southern California | 1,650–1,900 |
| Karnataka / Tamil Nadu | 1,500–1,750 |
| North India (Punjab, Delhi) | 1,400–1,650 |
| US Midwest | 1,300–1,500 |
| US Northeast | 1,200–1,400 |
| UK / Northern Europe | 850–1,100 |
| Germany | 950–1,100 |
Tracker vs. Fixed
| Geography | Fixed (kWh/kWp) | Tracker (kWh/kWp) | Tracker uplift |
|---|---|---|---|
| Arizona | 1,800 | 2,100 | +17% |
| Texas | 1,650 | 1,950 | +18% |
| India tropical | 1,600 | 1,900 | +19% |
| Spain | 1,650 | 1,920 | +16% |
Worked Example
100 MW plant in Bengaluru:
- Annual GHI: 1,920 kWh/m²/yr.
- POA after tilt (15°): 1,990 kWh/m²/yr.
- PR: 0.81.
Specific Yield = POA × PR
= 1,990 × 0.81
= 1,612 kWh/kWp/yrAnnual energy = 100,000 × 1,612 = 161 GWh/yr.
Year-by-Year Specific Yield (with degradation)
For a 0.5%/yr degradation rate:
- Year 1: 1,612 kWh/kWp.
- Year 5: 1,580.
- Year 10: 1,544.
- Year 25: 1,420.
- 25-year average: 1,510 kWh/kWp.
Common Mistakes
- Comparing specific yield without normalizing to PR or POA.
- Using year-1 number for 25-year revenue projections.
- Confusing DC specific yield (rare) vs. AC specific yield (standard).
- Ignoring availability/curtailment in real-world numbers.
Best Practices
- Report year-1, year-25, and 25-year average specific yield.
- Include statistical bands (P50, P90).
- Cite weather data source and EYA methodology.
- Compare to regional benchmarks for plausibility check.
Key Takeaways
- Specific yield = annual AC energy / DC nameplate, in kWh/kWp/year.
- Strong function of site irradiance, system efficiency (PR), and mounting (tracker vs. fixed).
- Benchmarks: 1,200–2,400 kWh/kWp globally; ~1,500–1,800 typical for utility-scale India and US sunbelt.
- Report year-1 and 25-year-average values for transparent investor communication.
- Specific yield × DC nameplate = annual revenue × tariff = headline project economics.
Frequently Asked Questions
10 commonly searched questions about Specific Yield.
What is specific yield?
Annual energy production per kW of installed DC nameplate, in kWh/kWp/year. A simple normalized metric for comparing solar plants across sites.
What's the formula?
Specific Yield = Annual AC Energy (kWh) / Installed DC Capacity (kWp). For a 100 kW DC plant producing 160,000 kWh/yr: specific yield = 1,600 kWh/kWp/yr.
What's a good specific yield?
US Southwest desert: 1,800–2,100 kWh/kWp. India tropical: 1,500–1,800 kWh/kWp. US Midwest: 1,400–1,600 kWh/kWp. UK/Germany: 900–1,150 kWh/kWp. India Himalayan: 1,200–1,400 kWh/kWp.
How does specific yield differ from PR?
Specific yield reports absolute output; PR is normalized to local irradiance. A high-irradiance plant has higher specific yield even with the same PR as a low-irradiance plant.
How does specific yield differ from capacity factor?
Specific yield = kWh/kWp. Capacity factor = average output / nameplate × 100%. Specific yield (kWh/kWp/yr) ÷ 8,760 = capacity factor (decimal).
Does specific yield account for degradation?
Reports vary. Year-1 specific yield uses fresh modules. 25-year average specific yield applies cumulative degradation, reducing the headline number by 6–10%.
Is specific yield AC or DC?
Typically AC delivered. Some literature uses DC specific yield (gross before inverter losses) but AC-delivered is the bankable convention.
How does tracker affect specific yield?
Tracker boosts specific yield 15–25% over fixed tilt. A site with 1,800 kWh/kWp on tracker may deliver 1,500 kWh/kWp on fixed.
Where do I find site-specific yield estimates?
PVsyst simulation, NREL PVWatts, Solargis Prospect, or commercial Energy Yield Assessments (EYA) from independent engineers.
Does specific yield include availability?
Yes — actual delivered energy includes downtime. Bankable EYAs report specific yield with 1–3% availability factor applied.
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