It maybe possible with little things like these to trim back your cost 20%.
Google lawn mowers that run on propane. A lot of tinkering going on to get some yard tools to run on something other than gasoline. Given the potential inroads with Shale Gas, maybe this is a place to look for opportunities...
The bigger question is water. I see you can get "Gray Water" systems ( i.e. taking shower water or washing machine water and using it for toliet flushing) from Canada for about $3,000, but I am not sure they are "certified" here in the States.
We have two shallow wells and one deep well. The deep well pump is killing us in the amount of electricity it uses. So we have a hand pump we are going to run a line into the house to the basement, for basic stuff and in case we lose power. When we have no power, we have no water. We’ve also been thinking that we should run the washing machine from the shallow well also.
I’ll check out the tromb wall building. Thanks for the info :)