Couple of questions relating to hot water heaters. I am building a new house and I am getting to the point where I have to buy and install a water heater. The house is located in a small New England town and our water is supplied from well.

1.I don’t need a back flow prevention valve or expansion tank, right?

2.This one might be a little more difficult; Gas or Electric? I was lean towards Electric because I don’t have an available flue to vent a gas water heater. But that means my generator (sometime we loose power for a couple of days (large snow storms)) would have to be hooked up to the heater. If I go with a gas heater, then I suppose I could use some type of power vent and vent it out the side wall or roof. The house’s boiler will be an efficient boiler and has a power vent kit. I guess I could vent both of these items through the roof. Any thoughts appreciated.

Ask you local building officials about local codes. Typically an expansion device whether it be a tank or a valve or a toilet fill valve is required on a closed system, meaning there is a check valve somewhere on the system to not allow water to return to the municiple system.
Seems to me the gas heater would be more effective and less expensive to operate. Is cost price an issue? If not, go with the gas water heater or even tankless. Put a battery backup on the tankless, possibly similar to a computer backup battery.

Doug thank you for the quick reply. I'll check with my local inspector but as I had mentioned I am on a well and not municiple system. Do people typically put a backflow (check valve) perventor when there water supply is from a well?

There isn't any real reason to need an expansion tank on a well. As long as you don't shut the supply valve off, the pressure tank works as your expansion tank. That doesn't mean your local code doesn't require it.

I fail to see the point of a battery back up for for a tankless heater. No power, no water to heat. On a new installation, I would look at some kind of a transfer switch making it easy to hook in a generator for power outages. If you instal a Square D breaker box, you can add an interlock plate for almost nothing. Other options are available. Do a search here perhaps on ''connect generator' There are several threads in electrical and lighting discussing different options. All of them would be cheaper done originally.

Do a search on ''tankless water heater'' and you will see where I on them.

Normoroy, I have never lived where a well was used. I have little experience on wells. I posted requirements about expansion devices to cover a lot of questions that could be asked. I do not know if a backflow is on a well but the big blue tank is a large version of an expansion tank.