Concentrated solar power: Efficiency
No better than PV by day, far better after dark
What this tab covers How much of the energy available is actually captured or extracted, in per cent: theoretical limits, laboratory records, typical new equipment and in-service averages, each with exactly what is being measured.Concentrated solar power plants turn about 14-16% of the direct sunlight reaching their mirrors into electricity over a year, similar to a PV field. Their advantage is storage: towers with 12-15 hours of molten salt can reach 68-79% capacity factors.
Chart: Efficiency ranges
Theoretical limit In service Record CommercialEfficiency by measure
| Measure | Range | Type | What is measured |
|---|---|---|---|
| Heat-engine ceiling at molten-salt temperature | 63.8%1 | Theoretical limit | Carnot limit for heat at 565 C rejected at 30 C (calculated); applies only to the heat-to-work step |
| Parabolic trough plants | 14 to 16%1 | In service | Direct sunlight to net electricity, annual average |
| Solar tower plants | 16%1 | In service | Same measure, about 16% |
| Linear Fresnel plants | 11 to 13%1 | In service | Same measure |
| Stirling dish systems | 25 to 30%1 | Record | Same measure; highest of any CSP design, but no storage |
| Capacity factor, new plants worldwide | 22%212 | In service | Annual output divided by full rated output all year, 2025 global weighted average; 30% in 2010 (2024, IRENA) |
| Capacity factor, towers with 12-15 hours of storage | 68 to 79%1 | Commercial | Same measure; Gemasolar in Spain (15 hours) was expected to reach 74% |
Where the energy is lost
| Step | Loss |
|---|---|
| Mirror reflectivity, shading, cosine and spillage losses | larger for Fresnel than for troughs (no share given)1 |
| Heat rejected by the steam cycle | at least 36% of the heat even in an ideal engine at 565 C (calculated), more in practice1 |
| Dry instead of wet cooling | about 7% less electricity1 |
CSP loses energy in two stages. Mirrors lose some light to imperfect reflection and to the angle between sun and mirror; the steam turbine, like any heat engine, converts only part of its heat to work. Hotter receivers raise this ceiling, which is why towers (molten salt at about 565 C) beat troughs, whose oil is limited to about 390 C. Only direct-beam sunlight can be focused, so CSP suits clear desert sites.
Sources
- Concentrating Solar Power: Technology Brief E10 IRENA and IEA-ETSAP, 2013
- Renewable Power Generation Costs in 2025 (Executive summary, Figure S1) IRENA, 2026
- Renewable Power Generation Costs in 2024: Summary (Table S1) IRENA, 2025