# Sustainability

## kg of coal

This indicator represents the kilograms of coal that would need to be burned to produce the same amount of energy as will be produced by the PV installation over the selected simulation period.

To calculate this equivalence, an average coal energy density of 29.3 MJ/kg is assumed. The energy density of coal is considered without including the losses that occur when transforming coal into electrical energy (in this step there would be a significant loss of ~60% of the energy).

## km in an electric car

This indicator represents the kilometres that can be driven in an electric car with the energy produced by the PV system during the selected simulation period.

To calculate this equivalence, a typical requirement of 160 Wh/km is assumed.

Since the value of this indicator can be very large, it is also used to generate other indicators that can be easier to understand:

Trips around the Earth in an electric car (assuming an Earth circumference of 40 075 km around the equator).

Trips to the Moon in an electric car (assuming the average distance between the Earth and the Moon is 384 400 km).

## kg of CO₂

This indicator represents the kilograms of CO₂ that would no longer be emitted into the atmosphere during the selected simulation period.

This calculation takes into account:

- Kilograms of CO₂ emitted to produce electricity according to country and according to the most recent data published by the European Energy Agency.
- The kilograms of CO₂ emitted in the module manufacturing processes, taking into account the cell type: monocrystalline (~340 kg/m²) and polycrystalline (~180 kg/m²).

## Trees planted

This indicator is calculated as the kg of CO₂ that would no longer be emitted into the atmosphere during the selected simulation period.

To calculate it, it is assumed that a typical tree absorbs about 10 kg of CO₂ in 1 year.

As an example, if the installation helps to avoid 5000 kg of CO₂ over 25 years, this would be equivalent to the CO₂ absorbed by 20 trees over the same period of time.