Sterilized water, is now commonly sold in handy water plants. It is filtered to almost distilled water purity, then sterilized to hospital standards. Use municipal water to refill your RV tank, and use this water for cleaning, rinsing, and bathing. Most municipalities in Baja that cater to beach campers, have water supplies that are safe to bathe and rinse in. Check with a neighboring camper to make sure.
Conserving electricity is a bit easier.
Most newer coaches have electronically controlled refrigerator freezers, and they consume battery power regardless of which energy source they're switched onto. Water pumps consume very little, but ventilation fans consume a lot of power. Even small fans will drain a battery if used continuously overnight. When the sun finally sets in Baja, set a camp fire and enjoy the evening outside. Disposal of gray and black water, should be done in an area that offends neither Mexicans, nor fellow tourists.