Irradiation unit converter and yield check

Converts solar energy per square metre between kWh/m², Wh/m², MJ/m² and langleys, per day or per year (a year is 365 days here). A design aid, not a data source.

1. Convert an irradiation value

Value (1,234.5 or 1.234,5 both work)

Unit

Per

Unit	per day	per year
kWh/m²	-	-
Wh/m²	-	-
MJ/m²	-	-
langley	-	-

Peak sun hours per day: - (kWh/m² per day divided by 1 kW/m²)

2. Back-of-envelope yield from panel-plane irradiation

Array size, kW DC at STC

Panel-plane irradiation, kWh/m²

Per

Performance ratio: an assumption (0.80 here), as a fraction or a percentage

Energy per day: - kWh

Energy per year: - kWh

Per kW of array, per year: - kWh/kW

Energy = array kW x panel-plane kWh/m² x PR. It is not a loss model.

Factors: 1 kWh = 3.6 MJ. 1 langley = 41,840 J/m². Daily values above 13.5 kWh/m² are flagged: a pvlib check found no day at any latitude above the atmosphere exceeded 13.49 kWh/m² on a horizontal surface.