Generally, the cost of conversion requires that a significant amount of fuel is consumed annually for the conversion to have a reasonable payback and this implies large vehicles with large engines as the best candidates. Smaller vehicles may also be converted but you need to do the math to have an idea if a conversion makes economic sense for your situation.
Let’s do a quick calculation to check the economics of an example:
| Description |
Calculation |
Result |
Units |
| Distance driven on a tank of gas | 600 | km/trip | |
| Litres used on trip | 60 | litres/trip | |
| Gasoline Mileage | 10 | km/litre | |
| Annual vehicle distance | 50,000 | km/year | |
| Propane economy as % of gasoline economy | 75% | conservative estimate | |
| Price of gasoline | 115 | ¢/litre | |
| Price of propane | 65 | ¢/litre | |
| Cost to drive trip distance on gasoline | = 60 * 115 / 100 | 69.00 | $/trip |
| Estimated litres of propane used on same trip | = 60 / 0.75 | 80 | litres/trip |
| Cost to drive trip distance on propane | = 80 * 65 / 100 | 52.00 | $/trip |
| Fuel Savings per km | = (69.00 - 52.00) / 600 | 0.0283 | $/km |
| Annual Savings | = 0.0283 * 50,000 | 1415 | $/year |
| Cost to convert vehicle | 5000 | $ | |
| Payback | = 5000 / 1415 | 3.53 | years |
Is this a good candidate? Maybe. Maybe not. It depends on how long you are planning to keep the vehicle and how much you hate buying gasoline. Put the above calculations in a spreadsheet and see if a conversion makes sense for you. Obviously, a small fuel-efficient gasoline-powered vehicle will push the number of years to pay back possibly longer than the life of the vehicle. Someone commuting to Toronto’s Pearson Airport from Fort Erie every day in this same vehicle will similarly have a very fast payback. Taxis and police cars operating in Toronto will also have a very fast payback as well.
Propane’s cost per litre needs to be far better than that of gasoline to help make up for propane’s lower energy content per litre and the cost of conversion. Propane’s price depends heavily on location so it would be quite cheap in Alberta and Toronto. Even though your gas mileage will definitely decrease due to the lower energy content per litre of propane but the more important cost per km would certainly improve. Typically, older vehicles with fumigation conversions could expect to get ~75% to 80% of their gasoline mileage, while new vehicles with injection conversions could expect ~80 to 85% of their gasoline mileage. If you don’t drive your vehicle very much annually or if you drive it where the difference between the cost of propane and gasoline is very small, the payback on the conversion may be so long that it will not make economic sense.