I just 2 months ago had almost the exact situation as you.

My unit:
8 y/o Trane 3 ton heat pump, 10.5 SEER (XL1000). Same contractor
billed, supposed to last about 10 years.

House would not cool properly in the afternoon when temp here in
Orlando got over 90. Called a service tech that found my Freon was
low due to a leak in my evaporator coil.

After speaking with the contactor about the evaporator coil I was
offered other options, the options we
1- Replace Evap coil, for $1280.00. Evap coil would have a 1-year
warranty.
2- Replace the air handler with a new variable speed Trane unit. This
would be about $1,700.00, have a 3-year warranty and the SEER rating
would remain at 10.85
3- Replace the whole system including the thermostat. There were
several choices of course but in the end we thought the 3.5-ton XL15i
(rated at 15.85 SEER) with the Trane Humidistat and a 10 year parts &
labor warranty would be the best fit for me. Price after rebates and
incentives $5,450.

I debated this and did TONS of research for about 10 days and decided
to replace the unit, it just seemed to make the most sense when you
look at the above options.

Anyway it's been 2 months since having it done and I could not be
happier. I have no problem getting 72 on a 92+ day, my electric usage
is slightly down and I have no worries for the next 10 years. That was
the big selling point in my decision.

Felix



wrote:
Really depends upon how often you have to top it off. I could liv with
getting it topped off at the beginning of the season each year if it
delayed getting a new system. Mors often thna that and I would want it
fixed if I could. Is it possible to fix a leaking indoor coil if you
can't get a new 10 SEER one?