Good morning all,

I stumbled on the forum this week and after reading through some of the posts/response have been impressed by the "well of knowledge" here.

OK having got the sucking-up out of the way, I'll get to the real reason for my post....

I live in Houston, TX and started experiencing some drop off in AC performance recently. So I called an AC contractor to service my AC systems, which have not been serviced since I bought the house four years ago. He serviced all 3 systems, recharged two with freon and informed me that the coil on the third was leaking badly and needed replacing imediately. He quoted me a price for a replacement. The price for the coil replacement was relatively expensive and got me thinking that perhaps I should look at replacing the entire system with a new higher efficency system.

The house is 16 years old and the AC systems are all original so presumeably getting close to, if not at the end of their economical service life.

I would like to evaluate the possible savings vs. cost for the various SEER units available. I don't know the size or SEER of the existing unit, I suspect it is 5 tons and 6-8 SEER. Component model numbers are -

Outside unit - Lennox HS18-651-8P
Furnace/air handler - Goodman GU125-5A Rev S
AC Coil - couldn't find a nameplate.

I would appreciate any guidance/thoughts on:
1) Am at at the economic service life of this 16 year old system system, that has been trouble free for me todate.
2) If I replace, how can I evaluate the cost/benefit of various SEER systems.
3) Can I replace one of my systems without causing problems for the others.
4) Any other suggestions welcomed.

Thanks in advance.