The sharp rise in diesel prices since the Iran War has materially altered the economics of replacing ageing heavy-duty diesel trucks, strengthening the business case for switching to cleaner fuels — particularly compressed natural gas (CNG) powered by renewable natural gas (RNG), according to an update to a 2025 report by the NGO Energy Vision.
Price shock reshapes cost calculus
Energy Vision says diesel prices have climbed about 60 per cent, to roughly $6.23 per gallon nationwide and about $8.15 per gallon in California. That spike has widened the price gap between diesel and lower-cost alternatives, making investments in CNG tractors that run on RNG far more financially attractive.
The updated analysis compares three clean alternatives for Class 7 and 8 heavy-duty trucks: new diesel models operating on renewable diesel (RD), battery electric vehicles (EVs), and new CNG trucks fuelled with RNG produced from organic waste. Each option offers air-quality and public-health benefits, but recent market moves have shifted the cost-benefit balance toward RNG.
"The economics of heavy-duty trucking have changed, strengthening the business case for adopting clean alternatives," said Michael Lerner, Energy Vision's director of research and publications and lead author of the report.
How the numbers line up
Energy Vision notes that RD carries lower upfront capital costs because it can be used in conventional diesel trucks, but its price tracks fossil diesel so recent increases have eroded that advantage. By contrast, RNG pricing is tied to CNG markets, which have been largely insulated from the conflict-driven spike in oil and diesel prices.
- RNG is now at least $3.50 per gallon cheaper than diesel in California and about $2 per gallon cheaper nationwide, the update says.
- Upfront capital expenditure for a new CNG tractor-trailer is around $75,000.
- Payback on that incremental investment can range from 1.3 years (with a $3.50-per-gallon diesel-to-RNG gap) to 2.8 years (with a $2-per-gallon gap).
- EV adoption in the heavy-duty segment remains tiny: of 5.2 million Class 7 and 8 trucks in the U.S. at the end of 2025, fewer than 3,000 were electric; annual additions are under 1,000 a year.
Those figures make RNG-fuelled CNG tractors a compelling near-term option for fleet operators focused on operating costs and payback periods, the report suggests.
| Option | Capex | Notes |
|---|---|---|
| Renewable diesel (RD) | Lower | Uses conventional diesel trucks; price tracks fossil diesel |
| RNG (CNG trucks) | ~$75,000 incremental per tractor | Payback 1.3–2.8 years depending on diesel-RNG price gap |
| Battery EVs | 2–3x diesel truck cost | High capex; adoption extremely limited |
Implications for fleets and policy
For fleet owners, the attraction of RNG is straightforward: when fuel accounts for a large share of operating costs, a sustained per-gallon saving of $2 to $3.50 can recover significant incremental purchase costs quickly. Short payback horizons also improve the case for financing or leasing arrangements that might otherwise make higher-capex technologies harder to justify.
Policy makers and regulators will watch such economic shifts closely. If fuel-price dynamics hold, public and private programmes that support RNG production, CNG refuelling infrastructure and vehicle conversion incentives may yield faster emissions and air-quality benefits than relying solely on the slower rollout of heavy-duty EVs.
That said, the report underscores that each pathway delivers health benefits and emissions reductions. RD eases the transition by working with existing diesel equipment; RNG offers rapid operating-cost wins where CNG infrastructure and RNG supply are available; EVs remain the long-term decarbonisation route but face near-term cost and deployment hurdles.
The Energy Vision update does not forecast future fuel prices, and the viability of any transition depends on regional fuel markets, infrastructure and policy supports. For Canadian fleets and provincial regulators dealing with cross-border supply chains, the report's findings add urgency to planning for both immediate cost pressures and longer-term decarbonisation goals.
As diesel volatility reshapes corporate calculations, the market may see more fleets weighing RNG-fuelled CNG tractors as a pragmatic bridge: cleaner than fossil diesel, cheaper at the pump today, and recoverable within a few years through fuel savings.
