Kilowatt-Peak — kWp
Energy & Electricity
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.
kWp is a measure of capacity, not a measure of energy. A 600 Wp solar module means the panel produces 600 watts under STC laboratory conditions; in Indonesia's tropical field, its actual output is always below the nominal figure due to cell temperatures higher than 25°C, non-ideal angles of incidence, surface dirt, and system losses.
As a practical indicator, 1 kWp of solar panel installed in Indonesia generally produces 3.5-4.5 kWh of electricity per day [NASA POWER 1984-2023], depending on geographic location and the assumed system performance ratio. This figure is the basis for capacity calculation: a household with a Rp 1 million monthly electricity bill usually needs a PLTS system in the 3-5 kWp range to cover daytime usage.
The term kWp must be distinguished from kVA (the unit of PLN connected power) and kWh (the unit of energy appearing on the bill). These three units are often confused in everyday discussion, even though they measure different things.
Indonesian PLTS Application Example
For a Greater Jakarta home with a connected power of 2,200 VA and a Jakarta PSH of 4.8 kWh/m²/day [NASA POWER 1984-2023], a 3.3 kWp PLTS capacity realistically produces ~12-13 kWh per day after multiplying by a performance ratio of 0.80. The typical investment cost in the Indonesian market is in the Rp 11-15 million per kWp range for a residential on-grid system without a battery.
Sources & References
- IEC 61215, Crystalline silicon terrestrial photovoltaic (PV) modules — Design qualification and type approval — IEC (2021)
- Surface meteorology and Solar Energy data set — NASA POWER LARC (1984-2023)
- SolarPlanner.id calculator methodology (placeholder — activation after LUMEN methodology sprint) — SolarPlanner.id (2026)
See Also
kWh
(Kilowatt-Hour)kWh, or kilowatt-hour, is the unit of electrical energy PLN uses to calculate bills: the amount of electrical power (in kilowatts) multiplied by the duration of use (in hours). One kWh is equivalent to running a 1,000-watt load for one full hour. In the non-subsidized R-1 tariff class for Q1 2026, each kWh is priced at Rp 1,444.70 [PLN tariff adjustment Q1 2026].
PSH
(Peak Sun Hours)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.
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.