If you live in the country, ice belt, tornado belt, hurricane belt or
earthquake belt, it's probably worth it. It'll be cheaper to do it
during construction than later. Natural gas is probably the worst
choice for fuel. In a lot circumstances where electricity goes out, so
does natural gas (hurricanes and earthquates are examples). Best is
propane if you have a big (100 gal plus) tank; this probably won't be
the case unless you live in the country. Propane is best because large
amounts can be stored indefinitely without degradation. Second best are
gasoline and diesel. Both fuels should have a "preservative" added to
them (you can buy it in autoparts stores). But even with a preservative,
it's best to use them within a year or two, and for most folks, this
means in the car or in yard/ag equipment. If you have a diesel car or
tractor, then diesel generator engines have more power per pound and
last longer. Diesel engines are harder to start in below zero (F)
temperature than gasoline engines. Otherwise, get a generator with a
gasoline engine, and you can turnover the fuel in your storage cans in
your car or lawnmower. Having your generator and car use the same fuel
means you can siphon some fuel out of the car to use in the generator if
you are in a prolonged outage as well as giving a way to turnover the
fuel in the storage cans before it is too degraded. Stay away from cheap
Chinese generators; getting service and parts for most of them is
impossible. Finally, test the generator regularly; don't wait for an
outage to find out it isn't working.

Mike

sprtan wrote:
While building my home, I was recently asked if I wanted to have a
natural gas driven back up power generator installed? Ostensibly to
provide back up power in the event of an outage.

My first question is whether or not anyone sees value in this.
Secondly, does it really matter whether I have it installed at time of
building or can I have one installed at a later time.