I am forced to install a new pressure tank at my summer home as the present one is shot. Our cottage does not have constant power and everything is powered by gas generators. It is on a mountain top lake. Constant power is not an option. I have a submersible jet pump in my well that supplies the water to the pressure tank. The pump is powered by a 4500 watt generator. Hence......the pump is only running when this very loud generator is turned on and the tank won't refill when the pressure drops without it being on.

The water system only feeds a shower and a kitchen and bathroom sink. Hot water is provided by a Bosch propane on demand water heater. Model 125K.

Now that it is time for a new tank....how large a tank should I install so that the generator does not have to be running full time for someone to take an average length shower? Keeping in mind that these Bosch water heaters will not heat the water once the pressure level drops below a certain point. I don't know what that pressure is off the top of my head and I am not at the cottage.

Any assistance or recommendation will be appreciated.

Thank you.