Workshop · How the scenario calculator works
What happens to fuel tax when less is filled up
The scenario calculator in the «Situation» tab works through a question that has been open in Bern for years: what happens to the 4,41 billion francs of mineral oil tax when more and more cars no longer need fuel? Anyone moving the sliders should know what runs underneath. Four points explain most of it.
The tax hangs on the litre, not on the price
Mineral oil tax is a fixed amount per litre. On petrol it is 43,12 centimes of base tax plus a 30 centime surcharge, on diesel 45,87 plus 30. For passenger car traffic the calculator uses a weighted mixed rate of 73,5 centimes per litre. That amount does not rise when the petrol price rises.
The whole mechanism follows from this. The federal government earns nothing from a higher price at the pump — on the contrary: a higher price lowers the quantity filled, and the quantity is the tax base. In 2025, 6,01 billion litres of road fuel were sold, producing 4,41 billion francs. The official BAZG time series shows 5,822 billion litres of petrol and diesel for the same year; the value used here lies 3,2 per cent above it. The calculator uses the higher one and reports the difference under «Method». Anyone who wants to know where the revenue is heading has to count litres, not francs.
A new registration is not a fleet
This is the confusion that distorts almost every discussion. From January to August 2026, 24,6 per cent of all newly registered passenger cars were purely electric, 36,9 per cent had a plug. The fleet looks different: at the end of 2025 there were 249’832 electric cars in a fleet of around 4,75 million passenger cars — a good 5 per cent. Together with plug-in hybrids, a good 8 per cent.
A passenger car stays on Swiss roads for a good ten years. Even if every new car were electric from tomorrow, the fleet would need a decade to follow — and it is the fleet that pays the tax, not the registration. That is why the tax gap in the calculator grows more sluggishly than the registration figures suggest. The «Shares» view shows both lines side by side.
The fleet pays the tax, not the new registration. A decade lies between the two.
Litres disappear along two routes
The drivetrain change is one route, and it is the visible one. The second runs quietly alongside: combustion engines are becoming more economical. The calculator assumes 7,0 litres per 100 kilometres and lets that value fall by 1 per cent a year.
- Drivetrain change. Every electric car replaces the litres of a combustion car. The big block — but it only takes effect once the vehicle is in the fleet, not at registration.
- Efficiency. One per cent less consumption per year, across the whole remaining combustion fleet. No headline, but cumulatively substantial.
- Other traffic and fuel tourism. 1,9 billion litres go to lorries, buses, agriculture and construction machinery, 0,32 billion to tank fills from abroad. Both items decline slowly in the model.
Against this stands an item that adds litres: the vehicle fleet is growing, by 0,8 per cent a year in the model. More cars, more kilometres. That this assumption lies above what the fleet figures of recent years show is recorded as a named gap under «Method» — it costs the model around 97 million francs a year.
What the per-kilometre charge captures and what it does not
The federal government wants to close the gap and on 26 September 2025 sent two equally ranked variants into consultation: a charge on the kilometres driven in Switzerland, or a tax of 22,8 centimes per kilowatt hour of charging electricity. The calculator covers only the first. Its rate is not flat: for passenger cars the draft law states 5,4 centimes plus 0,0026 centimes per kilogram above the reference weight of 2’383 kilograms — 5,4 applies to a vehicle of average weight, not to every vehicle. Battery electric vehicles and plug-in hybrids would be captured, the latter at half the rate; combustion cars without a plug continue to pay through the litre.
The charge therefore covers exactly one of the two routes. It does not capture the litres that disappear through more economical combustion engines: anyone needing 5 litres instead of 7 pays less mineral oil tax and no per-kilometre charge. The same applies to the collapsing fuel tourism. This is not a criticism of the proposal but a description of its reach — and the reason why the calculator reports shortfall and coverage separately.
What the calculator cannot do
- It is not a forecasting tool. It works through the assumptions set on the sliders — the forecast is the user’s own, the calculator only draws the consequences. Anyone setting the BEV share higher gets a bigger gap; that is not a prediction but the answer to «what if». Two readers with different views therefore get two different figures, and both are correctly calculated.
- It knows no political majorities. Whether a per-kilometre charge comes is not for it to decide.
- It carries heavy traffic only as a collective item. The performance-related heavy vehicle charge runs alongside and is not included.
- The fuel figures for 2019 to 2022 are reconstructed, not documented. From 2023 they come from Avenergy Suisse and the BFS.
Tax rates: BAZG, Mineral Oil Tax Act. Fuel sales: Avenergy Suisse. Vehicle fleet: BFS, road vehicle fleet at year end. Registrations: auto-schweiz, data ASTRA/IVZ, January to August 2026. Levy on electric vehicles: ASTRA, consultation draft of 26.09.2025 — draft E-Vehicle Levy Act (rates in annex 2) and draft E-Vehicle Tax Act (art. 8), plus the explanatory report. All assumptions of the calculator lie open in steuerbasis.json; what the model does not depict is in the gap register under «Method».
