Peak Sun Hours — PSH
Energy & Electricity
PSH, or Peak Sun Hours, is the number of equivalent sunlight hours during which an average irradiance of 1,000 W/m² is received on a horizontal surface per day. Its unit is kWh/m²/day. PSH is the core variable determining how many kWh per day each kWp of solar panel produces at a given location.
Technically, PSH translates total daily irradiance into equivalent hours at STC conditions. If a location receives a total irradiance of 4.8 kWh/m² in a day, that location is said to have a PSH of 4.8 hours — a figure used directly to multiply the installed capacity in order to estimate gross electricity production before derating.
Indonesia generally falls in a PSH range of 3.5-5.0 kWh/m²/day with an average of about 4.4 [NASA POWER 1984-2023], placing the country in the medium-to-high solar resource category. Regional variation is fairly significant: Jakarta and Bandung are at 4.8, Surabaya at 4.9, while Kupang and parts of East Nusa Tenggara exceed 5.5 due to low cloud cover and high aridity.
SolarPlanner's assets cover 121 NASA POWER coordinates (38 provinces + 83 cities) with 40-year climatology, so production can be estimated per location without crude interpolation.
Indonesian PLTS Application Example
A 5 kWp PLTS system in Jakarta (PSH 4.8 kWh/m²/day [NASA POWER 1984-2023]) with a performance ratio of 0.80 yields an estimate of: 5 × 4.8 × 0.80 = 19.2 kWh per day or ~7,000 kWh per year. An identical system in Kupang (PSH ~5.7) produces ~22.8 kWh/day — a ~19% difference purely due to the location's solar resource.
Sources & References
- Surface meteorology and Solar Energy data set (parameter ALLSKY_SFC_SW_DWN) — NASA POWER LARC (1984-2023)
- Indonesia Solar Resource Mapping — World Bank ESMAP (2017)
- SolarPlanner.id calculator methodology (placeholder — activation after LUMEN methodology sprint) — SolarPlanner.id (2026)
See Also
kWp
(Kilowatt-Peak)kWp, or kilowatt-peak, is the unit of nominal capacity of a solar panel measured at Standard Test Conditions (STC) — irradiance of 1000 W/m², a cell temperature of 25°C, and air mass 1.5 [IEC 61215]. In Indonesia, with a PSH range of 3.5-5.0 kWh/m²/day [NASA POWER 1984-2023], the kWp figure describes the theoretical peak output, not the actual daily electricity production under tropical field conditions.
Performance Ratio
(PR)Performance Ratio, or PR, is the ratio between the actual electricity produced by a solar PV (PLTS) system and the theoretical energy it should produce at STC conditions with the same irradiance. PR is a system-quality indicator commonly used by EPCs and IPP developers to monitor PLTS performance over its operating life.
Derating Factor
The derating factor is a reduction factor that makes a solar PV (PLTS) system's actual output lower than its nominal STC capacity. Derating covers cell-temperature losses, surface soiling, module mismatch, DC and AC cabling, and inverter efficiency. For Indonesia's tropical climate, the combined derating is usually in the 80-85% range.