Another good way to save energy on water heaters is to use tank
less on demand water heaters. You can find them online, or sometimes at
Home Depot. Since these systems may not be adequate during a shower, it
would be good to connect the plumbing in series, this way the output water
of one unit feeds input of the next unit. You will need to have an electrician
and the utility company wire in more separate heavy duty circuit breakers.
Having the home wired for more heavy duty circuit breakers may seem counter
intuitive to saving energy, but the energy used by these units is spent
for a short time at over 95% efficiency; where as the regular tank units
waste considerable amount of energy by radiating heat (due to low insulation)
during idle hours. Talk to your local PHYSICS professor to verify this,
and not your local numb nut handy man.