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Last updated: 24 March 2026
Dual-fuel diesel/CNG conversions were widely discussed a decade ago as a “low-carbon bridge” for commercial vehicles. A 2014 trade report described a two-year Emissions Analytics programme testing dual-fuel commercial vehicles on controlled routes to compare diesel-only versus dual-fuel running in real driving.
In 2026, the more useful question is: does dual-fuel still make sense for vans today — and what are the real costs and risks?
First: where “gas” has actually grown in the UK
Most UK growth in gas as a road fuel has been in HGV fleets using biomethane (Bio-CNG), supported by dedicated refuelling networks.
- A 2025 biomethane report says biomethane accounted for 3,246 vehicles on the road at the end of 2024 (heavy-duty focus)
- CNG Fuels’ station updates show 168 unique customer fleets refuelling across its network in the three months ending 30 Sept 2025
That doesn’t mean dual-fuel vans are “dead” — but the strongest business case and infrastructure investment has generally been in dedicated gas HGVs, not aftermarket dual-fuel van conversions.
What “dual-fuel” really means in cost terms
A dual-fuel diesel/CNG setup typically aims to substitute a portion of diesel energy with gas under suitable driving conditions. Your real cost outcome usually depends on five things:
1) Diesel displacement rate
How much diesel you actually replace varies by route profile, engine calibration, payload, temperature, and system operation. Low substitution means low savings.
2) Fuel availability and detours
If CNG refuelling isn’t convenient for your routes, detours and queuing reduce the financial benefit. This explains why gas adoption is concentrated along trunk routes and HGV corridors.
3) Conversion/maintenance cost and downtime
Aftermarket conversions add complexity (tanks, controls, calibration). Costs include installation, certification, maintenance capability, and downtime when specialist labour or parts are needed.
4) Payload and packaging penalties
Gas tanks and hardware can reduce usable payload or space, increasing operational cost if it forces extra trips or reduces tote/tool capacity.
5) The emissions wildcard: methane slip
Dual-fuel diesel/natural gas engines can be susceptible to methane slip. Methane is a potent greenhouse gas, so even with diesel savings, climate benefits can be offset if slip is significant.
So… is dual-fuel still worth considering for vans?
It can be, but it’s now a specialist fit rather than a default “low carbon” move. Dual-fuel looks most plausible when you have:
- High annual mileage
- Predictable route with reliable gas access
- Strong diesel substitution rate
- Maintenance/support plan with minimal downtime tolerance
If you can’t tick those boxes, alternatives are often simpler:
- Battery-electric vans for predictable urban routes
- Renewable diesel (e.g., HVO) where supply and policy allow
- Dedicated gas/biomethane primarily in heavier vehicles where infrastructure is strongest
Fleet insurance relevance
If you modify a van with dual-fuel equipment, insurers will want disclosure and may focus on:
- Vehicle modification disclosure (tanks, fuel system changes)
- Van parking location (theft/vandalism risk)
- Driver training and defect reporting
- Breakdown and recovery arrangements (specialist recovery may be needed)
Insurance savings should be treated as possible but not guaranteed. The most reliable benefit comes from reducing incidents and downtime.
Sources
- Motor Trade News (28 Apr 2014) — Emissions Analytics real-world dual-fuel commercial vehicle assessment
- UK Government report (2017) — Emissions testing of gas-powered commercial vehicles; methane slip and regulatory differences
- Green Gas Taskforce report (Oct 2025) — Biomethane in HGVs: 3,246 vehicles by end of 2024
- CNG Fuels station data (Oct 2025 update) — fleet refuelling customer numbers
- Emissions Analytics PEMS explainer/tag page — method background
- Academic study (2016) — greenhouse gas and emissions impacts of aftermarket dual-fuel configurations
VanCompare Editorial Team
The VanCompare Editorial Team produces clear, practical guidance on UK van insurance and related topics. We work with FCA authorised insurance providers and use insurer information where relevant to explain cover in plain English and help drivers make informed decisions.
Where relevant, our content is checked against publicly available UK guidance and information from sources such as the FCA and GOV.UK to help keep it accurate and up to date.
This content is for general information only and is not financial advice.
