My husband and I were pleasantyly surprised to find that we can survive on 1,500 gallons of water every 4 months. The biggest drain (hu-humm) on our water On Grid was the toilet. A composting toilet will run around $1,500, or alternately (and for MUCH less $$), you can compost it yourself on-site(there is a wonderful link on Humanure in another thread). Either way, you eliminate the need for watsewater treatment.
We use the grey water from our showers, dishes and hand washing to water native vegitation. We are still doing laundry in town at a coin op facility, but there are new high effeciency washers that use 8 gal. of water or less per load. I would hang my clothes to dry more than using a conventional clothes dryer, I think, but we haven’t gotten to that point yet. Where we are located, winter conditions are harsh, and it might make more sense to hang wet clothes inside (to prevent freezing and raise the humidity in the house).
I will see if I can find the solar water heater and the humanure handbooks that I was able to download and put those links here later.
Best of luck to you!!