We have a water heater, but we got rid of the shower head and pull up/out shower last year and now have a good old plastic jug which we use instead, so these days our washing procedure is to fill the shower/loo sink up with hot water and use one jug full of water to wet ourselves down, then follows a good all over soap up followed by 2 jugs to rinse off.
As we only ever used the shower previously as a wet down, turn off and soap up and then rinse off, we are both finding the new method to be almost as effective.
Phil