your lifestyle and mine are scarily similar (with my wife having the same comments, no doubt).
Count me in the same boat. Not all people can shower in 6L of water and tolerate or like cooler water or live the relatively low energy life we live.
But I question being able to cut my own consumption in half. In the winter my high-eff furnace is responsible for something like 50% of our electricity use. Yes lowering the home temperature (family members already complain about wearing an undershirt, shirt, sweater and being cold at 21C - what can I say a side effect of a vegetarian diet is that you loose a lot of body fat!) is possible; but not by 1/2 and have the home liveable. Although I do know people who keep their house around 60F (what 16C) in the daytime and cooler at night I could not tolerate it unless I was working (and I don't mean typing at a keyboard)!
Our electric water heater is about 1.5kWh/day - 1/5 of our total electricity use and we don't wash in hot but it would not be easy going down to 1/2 of our energy use.
Having embraced Voluntary Simplicity our TV is already relegated to the basement and the stereo system is gone.
The car is pretty well only necessary for convience and hauling the kids around (playing the game of racing between work and preschool to pick them up on time ..) - but it is 1/3 of our total personal carbon emisssions so it's something we could easily give up.
But there are tons of fuzzies. Sure we're got enough saved to last around 15 years without having to work; but what's going to happen to our savings? Hyperinflation? What's going to happen to our taxes (home taxes are about 1/6 of our total living expenses) and how much will it cost to repair the roof / furnace over such a time frame?