Solar CO₂ savings calculator

With the official German UBA average mix (344 g/kWh, 2025 edition), a 10 kWp system yielding 10,000 kWh avoids about 3.4 tonnes of CO₂ per year. Calculators that silently use a displacement factor of 600–700 g show nearly double — both bases are defensible, but they answer different questions, which is exactly why the choice is a visible switch here.

The average mix asks: how much CO₂ is in an average kilowatt-hour of grid power? The displacement factor asks: which power plant runs less when my system feeds in — usually a fossil one with higher emissions. For a personal balance the mix is customary, for system impact the displacement. A calculator using 690 g without explanation flatters its result by a factor of 2.

In the reference case after 1.2 to 1.7 years — depending on manufacturing emissions (400–600 kg CO₂e per kWp). Over a 25-year lifetime the system therefore works climate-positive for more than 93% of its time. The chart's curve deliberately starts below zero: the manufacturing debt belongs in the balance, not in a footnote.

Because it is the biggest lever of manufacturing emissions: modules from EU production cause about 40% less CO₂ than those from Chinese production per Fraunhofer ISE — mainly due to the electricity mix of cell manufacturing. The origin is rarely on the datasheet; asking the dealer for the cell origin yields information no salesperson volunteers.

Yes — and the calculator now quantifies it instead of merely mentioning it. The “account for a cleaner grid over time” switch lets the emission factor fall linearly to a year you choose. For 10 kWp in Berlin and the year 2045 (German climate law § 3(2): net greenhouse gas neutrality) the lifetime saving drops from 83,108 kg to 34,245 kg — 59 % less, an average factor of 142 instead of 344 g/kWh. This is not a forecast but a disclosed assumption; leave it unchecked and you keep the upper bound.

The average mix comes from the UBA time series (versioned dataset with validity window — precisely the source whose retroactive revisions our golden-test mechanism watches), the displacement basis and the manufacturing range are documented assumptions. The specification's reference case is reproduced under test.

From your location. The yield used to be an input field defaulting to 10,000 kWh — a number nobody could check. Now the same hourly simulation runs as in the annual-yield calculator: 10 kWp in Berlin gives 10,256 kWh per year, or 1,026 kWh per kWp. If you know your system's measured yield, the “enter annual yield manually” switch takes it.

Because solar only avoids as much CO₂ as the electricity it displaces causes. If grid power becomes greenhouse-gas neutral by 2045, a kilowatt-hour in 2044 avoids almost nothing — not because the system got worse, but because there is nothing left to displace. Averaged over 25 years that leaves 142 instead of 344 g/kWh. The bulk of the saving therefore falls in the early years.

No, quite the opposite. Even in the scenario 29,245 kg remain net of manufacturing — many times the 5,000 kg manufacturing costs. Energy payback stays at about 1.4 years. The point is a different one: the benefit is greatest NOW. Waiting gives away exactly the years in which a solar kilowatt-hour displaces the most.

It is deliberately simple and therefore traceable. The real path will not be straight — the last few percent of coal power are the hardest. So the calculator claims no forecast; it shows the span between two clear assumptions: a constant mix as the upper bound, a linear decline to your chosen year as its counterpart. The truth lies between them, and both edges are visible on the page.

Two, both readable in the law: the German Climate Protection Act (§ 3(2) KSG) requires net greenhouse gas neutrality by 2045. The Renewable Energy Act (§ 1(2) EEG) sets at least 80 % renewable electricity by 2030. Both are political goals, not guaranteed outcomes — which is why the year is your input in the calculator, not our fixed choice.