I totally agree with the retirement planning. Biggest mistake I made was getting solar systems that were not big enough. The battery storage system seems to be the answer but it's a bit new at the moment...like to see it around for a while, iron out the glitches and see the price of them reduce.
As I understand it from talking to the plumber; If you take two gas appliances, one natural (mains gas) and the other LPG (bottled gas) there is a difference in the size of the gas jets. You can convert a LPG appliance to a natural gas appliance by making the jets bigger (they drill out the jets on a barbie for example) but you can't do it the other way around and make the jets of a natural gas appliance smaller...plus there's a regulator for the conversion as the pressure is different.
I have had bayonet points fitted outside my houses and once the barbies need replacing I am going to get the new ones with bigger jets (some are available as a special order) and run them on mains gas to avoid having to worry about changing cylinders.