It depends a whole lot on how insulated your house is, where your pipes run (in a cold climate they shouldn't be in exterior walls... although of course sometimes they are anyhow) and whether you are on well water. Whether your house has any other form of heat. Also how long a power outage you are trying to plan for.
The pipes should only freeze if you have questionable insulation (always a good thing to invest in fixing anyhow) and/or they are in outside walls (also may be worth $ to fix), or if the power outage is quite long in quite cold weather. The more you can trickle water thru pipes, the less of a problem freezing is. Also, if just part of your plumbing system is vulnerable (e.g. an exterior-wall run of pipe up to a cold upstairs bathroom) you can install a valve by which that part can be turned off and manually drained in the event of what looks to be a prolonged outage.
So unless you have *unusually* vulnerable pipes, you have to ask what am *I* going to be doing, if the house is that cold for that long?
A woodstove or soemthing like that might make as much or more sense
As far as generators, please make sure to hire a professional electrician to install it if there will be things (furnace, well pump, fridge circuit, whatever) to which it is permanently wired (as opposed to smaller generators where you just run a cord into the house and plug things in by hand). If it is not done EXACTLY RIGHT (which btw can cost as much as the generator did) you can wind up inadvertantly electrocuting (like, fatally) unsuspecting power company linemen
It is not something to fool with; make sure it is done RIGHT.
Have fun,
Pat
