Although your system is 15 years old, it's still very efficient. You aren't
going to save much money in operating costs with a new gas system. Keep it
properly maintained, and look into getting a service contract from a company
you trust. If it starts giving you trouble, that's the time to replace it.
Geothermal units are expensive to install, and (depending on the type) can
require a lot of yard work after it's installed. A geothermal will save you
money, but the payback could take a long time, considering what you have
now.

"Jay Stootzmann" wrote in message
news:XO%uf.685178$_o.38838@attbi_s71...
I currently have a relative high efficiency gas furnace and air
conditioning
system.

The gas furnace exhaust is via a plastic pipe. Though the motors for the
furnace fan and the AC are not multispeed so they are not the highest
efficiency available but in 1991 they were pretty good for that time.

The furnace and AC are into their 15th year and it's my understanding that
the useful life of these items is usually 15-20 years.

I'm wondering at what point I should go ahead and replace my system? With
the price of Gas continuing to go up should I be looking sooner rather
than
later?

When I replace it should I go with another high(er) efficiency gas furnace
and AC [location is north central Illinois]?

or Should I be looking at replacing with a geothermal system?

Any thoughts, comments, things to look for, etc.

Thanks.