Approx. Cooling Energy $avings
(Adjust to $uit your $ituation)
SEER 12 vs 17 = ~71% as much energy
~10 hours /day
~50 kw-Hr / day
1500 kW-Hr/ month
$0.10 $ / kW-Hr
$150.00 Monthly Cooling Cost
$44.12 Savings per month at 29% (100- 71)
$220.59 per year
If the 5-ton A/C unit runs for
10 hours each day for 150 days (30 days x 5 months),
your annual cooling cost savings would be ~$220.
It seems like A/C might be 45% to 62% of total electric bill. At 14 hours per day run time, cooling cost would be $210 per month, and
savings would be $61 per month for about 5 months (MAXimum, unless you are in Phoenix) per year.
Total annual cooling hours in the VERY Simplified Example
above is 1,500 hours
which may vary significantly due to
weather in your specific area
and A/C unit performance.
System price ~$10,000 simply to have
more efficient unit ... Pay-back 45 years.
More realistic comparison,
system price greater than the
cost of a 12 SEER replacement:
Say $3,000 is approximate cost
for upgrade from 12 to 17 SEER.
Pay-Back = 13.6 years.
Obviously, other A/C performance and building envelope enhancements should be evaluated
prior to equipment SEER upgrade by itself
as others will comment here.