A while ago I switched over from an oil-fired indirect tank to an electric water heater. We had a short power outage the other day, which got me thinking of how to operate the electric water heater in an outage. I have a 7500 w continuous gasoline generator that can run the deep well pump. I figure turn that off, and heat up the water and then turn the water heater off and then take showers, etc. Thinking of (precious) fuel consumption, how long does it take to heat up a tank of water? I could re-align valves, and place the indirect tank back in service, but that'd take some time and thought and then I'd have to drain the tank, etc, ie, laziness factor. Thanks.