Global horizontal irradiation

What this step does

The first line of the loss diagram: the sunlight that fell on a horizontal surface at the site over the year, summed from the weather file. Every irradiance row below it is a gain or a loss on the way from this number to the light that reaches the modules.

The math

$$H_h = \frac{1}{1000}\sum_i G_{h,i}\,\Delta t \tag{1}$$

where

Symbol	Meaning	Unit
$H_h$	the global horizontal irradiation over the year	kWh/m²
$G_{h,i}$	the global horizontal irradiance of timestep $i$	W/m²
$\Delta t$	the length of one timestep	hours

Reading the number

A total, positive. The weather file alone sets it, the same for a utility plant and a rooftop system at one site. It is about 1,000 kWh/m² a year in northern Europe, 1,400 to 1,700 kWh/m² in the central United States and 2,000 to 2,500 kWh/m² in desert regions.

API

loss.glob_hor

Symbols follow the symbol registry.