It doesn’t take much research to conclude that converting our cars to LPG would be an excellent plan. Or does it? This is a quick sketch of LPG vs petrol for a (light) commuter here in Sydney.
Yes, most modern engines will happily use LPG.
LPG Autogas Australia is the main advocacy site here in Australia.
The federal government is offering a $2,000 rebate for the conversion of private petrol or diesel cars, so that should be the bulk of your costs – out of pocket expenses seem to commonly be around $600.
So how long will it take to make the $600 back? Let’s see …
Using Shell’s 28 day average :
ULP 118.6 cents per litre, but let’s discount this for good shopping skills to 110.
LPG is more difficult to find long term prices, but let’s go slightly high and use 55 cents per litre.
Now for efficiency. According to Greenfleet ULP has 38% higher energy density than LPG, so we’ll need to use 38% more LPG for the same distance travelled.
So if we increase the cost per litre by that 38% to account for the extra we need to use, we get (55 * 1.38) 75.9 cents.
This is still (110 – 75.9) 34.1 cents per litre cheaper.
Still with me? Good, just a little more : we now need to recover $600 in chunks of 34.1 cents which means we will break-even after around 1,760 litres.
Since I have been using somewhere between 15 and 20 litres per week for my limited travels, this would be recovered in around two years of driving.
Clearly the LPG conversion makes more sense the more kilometres you drive.
What about other situations? If we re-use the pricing figures above, at only 40 litres per week you would recover your money in 44 weeks.
For all the calculations, see my spreadsheet online.
[Follow up done 6 months down the track – savings are getting better!]