CNG (Compressed Natural Gas) Vehicle Conversion: Pros, Cons, and Economics

How CNG Vehicle Conversions Work

A CNG conversion adds a secondary fuel system to a gasoline vehicle (bi-fuel) or replaces the gasoline system entirely (dedicated CNG). CNG (compressed natural gas) is stored at 3,600 psi in high-pressure tanks, then regulated down to engine inlet pressure. Gaseous CNG enters the intake system through a mixer or sequential injectors.

Fuel Cost Comparison

CNG is priced by the GGE (gasoline gallon equivalent). Nationally, CNG averages $2.00–$2.80/GGE vs $3.50+ for gasoline — a 20–40% cost advantage. In areas with abundant natural gas (Oklahoma, Texas), CNG can be as cheap as $1.50/GGE. Home refueling via a Phill unit connected to your home gas line costs approximately $1.00/GGE when accounting for equipment.

Vehicle Selection for CNG

Best candidates for CNG conversion: trucks and vans that travel high annual mileage on predictable routes near CNG stations. High-roof cargo vans (Ford Transit, Ram ProMaster) have space for large CNG tanks. Pickup trucks can carry tanks in the bed with optional toolbox integration.

Conversion Costs

An EPA-certified bi-fuel CNG conversion costs $6,000–$12,000 professionally installed. Home fueling unit (FuelMaker/BRC): additional $3,000–$5,000 installed. Payback at $1.50/GGE savings and 25,000 miles/year: 4–6 years.

CNG vs HHO

CNG is a complete alternative fuel; HHO is a combustion supplement to existing fuel. CNG offers larger fuel cost savings where access exists; HHO is immediately available to any vehicle without infrastructure dependency.