Runing water=heater from generator.
Re: Electric water heaters. An additional thought regarding reducing the load placed on your generator when powering an electric water heater.
As mentioned before if you disconect the uper element, then the power draw would be half normal, and the heating time would be TWICE NORMAL.
If you have two heating elements (almost all water heaters have two heating elements) and you rewire them in series (perferably by means of a high power rated (double pole doubel throw) switch that is hiden so no one (like a kid) throws it and puts the water heater back into full wattage) you can reduce the load to one fourth that of normal. The heating time will be FOUR TIMES NORMAL.
Also note that if your water heater is a 240 volt unit and you run it on 120 volts, the power the heater would draw would be only 1/4 of normal. The heating time would be FOUR TIMES NORMAL. This is because at 120 volts the curent draw would be half that of normal. And since the voltage is only 120 (half that of normal) and the wattage is AMPS x VOLTS the wattage draw would be 1/2 x 1/2 = 1/4. This is if you ran a 240 volt water heater on 120 volts and left both heating elements conected.
If you ran a 240 volt water heater on 120 volts and you disconected the uper element then the power draw would be 1/8 that of normal. The heating time would also be EIGHT TIMES NORMAL.
If you were to put two 240 volt elements in series and run them on 120 volts the power draw would be 1/16 normal. The heating time would be 16 TIMES NORMAL. This is geting a bit long and might not be enough when adding on heat loss to ambient. However if you realy want to cut back on power draw and you can get by with very long hot water tank recovery time (not too many people using the hot water) this might be worth a try.
Reducing the power draw might be raealy valuable since it would allow you to use a small generator that gets many hours from one gallon of gas such as the HONDA eu2000i .
I have gas hot water. If I had electric I would try the reduced wiring and after determining which worked best for my requirement I would install a hiden switch with a long life low power draw indication light in plain view that would remind me to turn it back to full power when once again runing from the grid. You would require a three pole double throw high power switch (hard to find) so you would have a pole for the light.