Study: Germany’s 12 o’clock rule raised petrol margins by about €0.06 per litre, study finds
Study by ZEW and DICE finds Germany’s 12 o’clock rule increased petrol margins by ~6 cents per litre in early April, with regional and retailer differences.
The 12 o’clock rule for fuel price increases has corresponded with higher petrol margins in Germany in the weeks after its introduction, according to a new joint study by ZEW Mannheim and the Düsseldorf Institute for Competition Economics (DICE). The research, covering two weeks before and two weeks after the reform took effect on April 1, 2026, finds average margins on Super petrol rose by roughly €0.06 per litre immediately after the rule began to apply. The study raises fresh questions about the reform’s effectiveness in lowering consumer prices amid an ongoing energy crisis.
Study authors and headline findings
Leona Jung of DICE and Jacob Schildknecht of ZEW reported that the policy package accompanying the 12 o’clock rule has not yet reduced the overall price level for petrol.
Their analysis shows that in the first fortnight after April 1, net retail margins for Super petrol were on average six cents higher per litre than in the two weeks before the rule.
DICE director Justus Haucap noted the effect was not uniform across fuels or firms, and that diesel margins fluctuated strongly during the observation period, complicating definitive conclusions for that product.
Petrol versus diesel: differing patterns
The study highlights a clearer and more consistent uptick for petrol than for diesel during the sampled period.
Researchers attribute the weaker diesel signal to larger short-term volatility in wholesale and retail diesel pricing, which made it difficult to isolate a systematic margin increase within the two-week window.
They caution that signs of similar behavior for diesel exist but require a longer observation period and further analysis to quantify reliably.
Regional concentration of price rises in southern Germany
The analysis shows the most pronounced petrol margin increases occurred in southern Germany, where prices rose more sharply in the days following the reform.
Authors suggest this regional variation may reflect higher average per-capita incomes and greater willingness to pay in the south, alongside differences in supply-chain costs and regional procurement that affect station-level pricing leeway.
These factors, combined with local market structure, appear to have amplified margin adjustments in certain areas.
Smaller chains and independents saw the largest increases
The study finds that independent stations and smaller regional chains recorded the biggest margin increases after the 12 o’clock rule was implemented.
By contrast, larger national operators exhibited smaller margin shifts, a pattern the researchers link to the greater legal and reputational scrutiny such firms face and their exposure to antitrust review.
This divergence suggests that market structure and expected regulatory oversight moderate how firms translate constrained price-change windows into retail margins.
Regulatory reaction and ongoing investigations
Germany’s Federal Cartel Office (Bundeskartellamt) opened investigations in early April 2026 into potential breaches of the new rule and into suspected coordinated pricing behavior.
DICE and ZEW note that the observed margin pattern — particularly among smaller operators — is one reason competition authorities are monitoring the market closely.
Regulators will need to determine whether higher margins reflect legitimate cost pass-throughs or strategic adjustments to the once-daily price-increase constraint.
Methodology and data sources
Researchers used price records from the Market Transparency Unit for Fuels, comparing 14 days before and 14 days after April 1, 2026, to construct the study window.
Retail net prices were measured against wholesale benchmarks from the Amsterdam–Rotterdam–Antwerp (ARA) region to estimate changes in station-level margins.
The authors stress that the short observation period limits longer-term inference and call for continued data collection to assess whether the early effects persist or dissipate.
Context of the reform and prior criticism
The 12 o’clock rule, introduced as part of an initial government package to ease energy-market strains, permits stations to raise prices only once per day at 12:00 CET, while allowing more flexible reductions.
Critics warned before implementation that the measure, modeled after a policy used in Austria, might incentivize preemptive or synchronized price increases and therefore raise retail prices rather than lower them.
Early cross-border comparisons with neighboring EU countries showed petrol prices in Germany rose particularly sharply in the days immediately after the rule took effect, a pattern the study corroborates for the sampled period.
The study’s findings do not presuppose intentional collusion but do indicate that timing restrictions on price increases interact with market structure and consumer demand in ways that can lift margins. Continued monitoring, broader datasets and longer observation windows will be needed to judge whether the initial effects identified by ZEW and DICE represent a temporary adjustment or a sustained change in pricing behavior that warrants further policy action.
