CO₂ Savings
How the engine estimates the CO₂ reduction achieved by solar panels and batteries, and how to translate it into tangible equivalents.
The formula
CO₂ savings are derived from the difference in grid electricity between the baseline and optimized scenarios:
annual_co2_savings_kg = (baseline_grid_import - optimized_grid_import) × emission_factor
The grid import values come from the 8,760-hour simulation. Every kWh of solar energy consumed on-site (or stored in a battery for later use) is a kWh not drawn from the grid.
Emission factor
The engine uses a fixed Dutch grid emission factor:
emission_factor = 0.4 kg CO₂ / kWh
This value represents the average carbon intensity of the Dutch electricity grid. It is applied uniformly across all hours — the engine does not use hourly marginal emission factors.
The 0.4 kg/kWh figure is a rounded average. Actual grid emissions vary by hour (coal-heavy hours can exceed 0.6 kg/kWh, wind-heavy hours can drop below 0.1 kg/kWh). Using a fixed factor provides a stable, reproducible estimate.
Real-world equivalents
The API response includes several equivalents to make CO₂ savings tangible for end users:
| Equivalent | Conversion | Meaning |
|---|---|---|
| Trees planted | co2_savings_kg / 21 | An average tree absorbs ~21 kg CO₂ per year |
| Car km avoided | co2_savings_kg / 0.12 | An average car emits ~0.12 kg CO₂ per km |
| Flights avoided | co2_savings_kg / 255 | A one-way AMS–BCN flight emits ~255 kg CO₂ per passenger |
Example
A system that reduces grid import by 3,000 kWh/year:
- Name
co2_savings- Type
- kg/year
- Description
3,000 × 0.4 = 1,200 kg
- Name
trees_equivalent- Type
- trees
- Description
1,200 / 21 = 57 trees
- Name
car_km_equivalent- Type
- km
- Description
1,200 / 0.12 = 10,000 km
- Name
flights_equivalent- Type
- flights
- Description
1,200 / 255 = 4.7 flights
Response excerpt
{
"co2": {
"annualSavingsKg": 1200,
"equivalents": {
"treesPlanted": 57,
"carKmAvoided": 10000,
"flightsAvoided": 4.7
}
}
}
Lifecycle projection
The scan result also provides a 25-year lifecycle projection:
lifetime_co2_savings_kg = annual_co2_savings_kg × 25
The 25-year horizon matches the typical warranty and expected lifespan of modern solar panels. The projection assumes:
- Constant annual consumption pattern
- No panel degradation (conservative: real panels degrade ~0.5%/year)
- Constant grid emission factor
As the grid becomes greener over time, the marginal CO₂ benefit of solar will decrease. The lifecycle projection is a conservative upper bound based on today's grid mix.