What changed at the turn of the year

Until 2025 the CO₂ price was fixed at 55 euros per tonne. From 2026 the German government no longer sets a single figure — the price moves within a corridor of 55 to 65 euros per tonne (MDR, 7 January 2026).

That reads like a footnote to energy policy. For a rental fleet it is not.

The amount sits in the litre price, not on the quote

At 65 euros per tonne, the CO₂ component is around 20.7 cents per litre of heating oil (TotalEnergies, 2026). For diesel used in combustion engines the share is in the same order of magnitude, because it is tied to the carbon content of the fuel, not to what the fuel is used for.

The real point is different: this amount never appears as its own line on a quote. It sits inside the litre price. Anyone who calculates the fuel share with a rule-of-thumb price per litre and leaves the corridor out of the maths carries the difference themselves — on every generator-day they rent out.

What this means in practice

Three things change. Everything else stays.

First: the corridor belongs in the calculation, not in hope. If the price moves between 55 and 65 euros, the honest calculation is a range, not a point value. A quote built on the lower end looks cheaper and is not.

Second: the fuel share becomes a variable. For a generator running over weeks, the difference between the lower and upper edge can be larger than the margin. Whoever does not show it only notices at month end.

Third: the diesel-versus-battery comparison becomes more sensitive. Not because the battery gets cheaper, but because the other side gains a line item it did not have before. When comparing the two, set the fuel price as a range — otherwise you are comparing a fixed number with a moving one.

What does not follow from this

The CO₂ price does not turn a diesel generator into a bad investment. It shifts the ratio; it does not decide it.

Whether a battery unit actually fits a given site still depends on three things: the connected load of the tools, the time between two charges, and whether there is a charging source on site at all. Where those three are not settled, the generator remains the more honest answer — even at 65 euros per tonne.

What changes is the direction of the pressure. And the fact that the line item now has a name.

Which line is still missing from your rental quote — the fuel price, the maintenance, or the standing time?