FIY: In the state of California, where electricity costs $0.286 / kWh, it would cost $2,547 to run your 14 SEER central AC for a whole year. A more efficient 18 SEER central AC would cost $2,063 per year.

The saving from upgrading to a higher efficiency system would be $484 per year, and it will take just 3.6 years to recoup the extra upfron cost.