Here are two quotations you might wish to pass along to your friend Charles:
“Be the change you want to see in the world.”
M. K. Ghandi
“Example is not the main thing in influencing others, it’s the only thing”
Albert Schweitzer
When Charles is seen riding his bicycle or walking to work, flying economy class with his fellow Brits, and living in an energy-efficient home, people will at least have to credit him with sincerity. Until then, he’s just the British version of Al Gore, held in contempt for his “do as I say, not as I do” rhetoric.
And he does a great deal to be energy efficient. Some of which is public. Some of which is not.
I won't discuss what I know of his travel arrangements as there are security implications, except for those things that are already public knowledge.
That is that the Prince does fly on normal commercial jets with British Airways whenever possible. Because he is an assassination risk (and therefore his presence on the plane could endanger other passengers - and that's no joke, I've stood within metres of him as somebody ran at him firing a pistol - fortunately it turned out to be a starting pistol) this is only done in cases where it can be done without it being known in advance that he will be on the aircraft - if he's travelling to a major overseas event it generally isn't possible. The only member of the Royal Family who never flies commercially is the Queen. Everybody else does so wherever it is feasible and possible for them to do so. That's public knowledge, but it's not given a great deal of publicity for security reasons. The Prince has expressed a desire to fly economy class, but this was vetoed by his security - it's more expensive and complicated to background check an entire economy class cabin, and his security staff are entitled to travel business class under their terms of employment with the Metropolitan Police.
He does walk to work in most cases (it would often be ridiculous to do otherwise, as his office is in the same building he lives in, but he also walks further afield wherever possible), but again for security reasons and reasons of time (he generally undertakes a number of public engagements every day, and the time to travel between them makes anything other than vehicular transport impossible) he does often travel by car. His main personal vehicle is a 40 year old Aston Martin that he paid to have converted a few years ago to run on biofuel. The cars he uses for official duties are armoured for security purposes and it is currently impractical to produce an energy efficient armoured vehicle, but he has directed quite a lot of money towards research to change that.
These are all facts - but they are not facts the media will normally tell you.